Exams › SSC CGL (Prelims) › General › Percentage
73 questions with worked solutions.
Q1. If 40% of P = 0.5 of Q = \(\frac{1}{8}\) of R, find P : Q : R.
Answer: 5: 4: 16
Let $40\%$ of $P = 0.5$ of $Q = \frac{1}{8}$ of $R = x$. Then $P=\frac{x}{0.4}=\frac{5x}{2}$, $Q=\frac{x}{0.5}=2x$, and $R=8x$. So the ratio is $\frac{5}{2}:2:8 = 5:4:16$.
Q2. Evaluate: $15\frac{1}{3}\%$ of 480 km + $58\frac{1}{3}\%$ of 300 km.
Answer: 248.6 km
$15\frac{1}{3}\% = \frac{23}{150}$, so its value on 480 km is $480\times\frac{23}{150}=73.6$ km. Also, $58\frac{1}{3}\% = \frac{7}{12}$, so its value on 300 km is $300\times\frac{7}{12}=175$ km. Adding gives $73.6+175=248.6$ km.
Answer: ₹ 56,000
Commission per laptop is 3% of ₹40,000 = ₹1,200, so 4 laptops give ₹4,800. Commission per printer is 8% of ₹8,000 = ₹640, so 10 printers give ₹6,400; weekly total = ₹11,200. For 5 weeks, total commission = ₹11,200 × 5 = ₹56,000.
Answer: 16.64%
The area of a circle is proportional to the square of its radius. If the radius increases by 8%, the new area becomes $(1.08)^2 = 1.1664$ times the original area. So the percentage increase is 16.64%.
Answer: 2.4% increase
Let the original expenditure be 10 units, split as 3, 5, and 2. After the changes, the new expenditure becomes 31.08 + 51.04 + 20.90 = 10.24 units. So the total expenditure increases by 0.24 units, i.e. 2.4%.
Answer: 4.2% increase
Let the original budget be 10 units, split as 4, 3, and 3. After changes, the new cost becomes 4×1.12 + 3×1.08 + 3×0.90 = 10.42 units, so the increase is 0.42 units out of 10, i.e. 4.2%.
Answer: 27,000
Let men be \(m\) and women be \(40000-m\). After the changes, total becomes \(0.96m + 1.12(40000-m)=40480\). Solving gives \(m=27000\).
Answer: 34091
If 13,500 is 55% of valid votes, then valid votes = \(13500/0.55\). Since 4% of polled votes were invalid, valid votes are 96% of polled votes. Then polled votes are 75% of eligible voters, so the eligible voters can be found by reversing these percentages.
Answer: 2088
Total employees = 120, so each employee kit has \(12\%\) of 120 = 14.4 items. Each supervisor kit has \(20\%\) of 120 = 24 items. Total items = \(120\times14.4 + 15\times24 = 1728 + 360 = 2088\).
Answer: ₹ 240
The extra discount is the increase from 12% to 18%, which is 6% of ₹4,000. So the extra discount = 0.06 × 4,000 = ₹240.
Q11. Evaluate: 75% of 400 - 32.5% of 200 + 18% of 300
Answer: 289
75% of 400 = 300, 32.5% of 200 = 65, and 18% of 300 = 54. So the value is 300 - 65 + 54 = 289.
Answer: 11.6
The student got 30 correct in Physics, 38.5 in Chemistry, and 31.5 in Biology, totaling 100 correct answers. Passing requires 62% of 180 = 111.6 correct answers, so the shortfall is 11.6.
Q13. 4.5% of 600 = ?
Answer: 27
4.5% means $\frac{4.5}{100}$. Multiplying by 600 gives $0.045\times 600=27$.
Answer: 12.5%
After an 18% discount on ₹30,000, the price becomes ₹24,600. The final selling price is ₹21,528, so the second discount is ₹3,072 on ₹24,600, which is 12.5%.
Q15. Eighty percent of a number is 20 more than three-fifths of that number. Find the number.
Answer: 100
Let the number be \(x\). Then \(0.8x = \frac{3}{5}x + 20\). Solving gives \(0.2x = 20\), so \(x = 100\).
Q16. A sum of money amounts to ₹13,225 in 2 years at 15% compound interest annually. Find the principal.
Answer: ₹10,000
Under compound interest for 2 years at 15% per annum, amount = \(P(1.15)^2\). So \(13225 = P \times 1.3225\), giving \(P = 10000\).
Q17. In a class of 60 students, 40% are boys. If 75% of the boys passed, how many boys failed?
Answer: 6
40% of 60 students are boys, so the number of boys is 24. If 75% of them passed, then 25% failed. 25% of 24 is 6, so 6 boys failed.
Q18. If 30% of \((A + B)\) = 60% of \((A - B)\), then find the ratio \(A:B\).
Answer: 3:1
Given 30% of \((A+B)\) equals 60% of \((A-B)\), we get \(0.3(A+B)=0.6(A-B)\). Solving this equation gives \(A=3B\), so the ratio is \(3:1\).
Answer: 20%
If the second discount is 10%, then the price before the second discount must be ₹10,800 ÷ 0.9 = ₹12,000. This means the first discount reduced ₹15,000 to ₹12,000, i.e. by ₹3,000. So the first discount percentage is 3000/15000 × 100 = 20%.
Q20. If P is 40% more than Q, and Q is 25% more than R, find the ratio P:R.
Answer: 7:4
If $Q$ is 25% more than $R$, then $Q=1.25R$. If $P$ is 40% more than $Q$, then $P=1.4Q=1.4\times1.25R=1.75R$. Therefore, $P:R=1.75:1=7:4$.
Q21. If 20% of \((A + B)\) = 50% of \((A - B)\), then find the ratio \(A:B\).
Answer: 7: 3
The equation is \(0.2(A+B)=0.5(A-B)\). Simplifying gives \(2(A+B)=5(A-B)\), so \(2A+2B=5A-5B\), hence \(7B=3A\). Therefore, \(A:B=7:3\).
Q22. If 25% of P is equal to 40% of Q, what is the ratio P:Q?
Answer: 8: 5
Given 25% of P = 40% of Q, we have \frac{25}{100}P = \frac{40}{100}Q. This simplifies to 25P = 40Q, or P/Q = 40/25 = 8/5. Hence, the ratio P:Q is 8:5.
Answer: 15%
After a 20% discount on ₹1200, the price becomes ₹960. The final price is ₹816, so the second discount is \(960-816=144\), which is \(144/960=15\%\).
Q24. If 20% of \(P\) = 15% of \(Q\) = 12% of \(R\), find \(P:Q:R\).
Answer: 3: 4: 5
Let the common value be \(k\). Then \(P=\frac{k}{0.20}\), \(Q=\frac{k}{0.15}\), and \(R=\frac{k}{0.12}\). This gives \(P:Q:R = \frac{1}{0.20}:\frac{1}{0.15}:\frac{1}{0.12} = 5:\frac{20}{3}:\frac{25}{3} = 15:20:25 = 3:4:5\).
Q25. If 20% of m is equal to 80% of n, what is the ratio m:n?
Answer: 4:1
Given \(20\%\) of m = \(80\%\) of n, we have \(0.2m = 0.8n\). Dividing both sides by 0.2 gives \(m = 4n\), so the ratio m:n is 4:1.
Q26. A number is increased by 25% and then decreased by 25%. What is the net result?
Answer: 6.25% decrease
If the original value is 100, increasing by 25% gives 125. Decreasing 125 by 25% gives 93.75. This is 6.25% less than the original 100, so the net result is a 6.25% decrease.
Answer: ₹ 40,000
After charity, 75% of the salary remains. Of this, 20% goes to investments, leaving 80% for education and travel. Since travel is 3/8 of that remaining amount and equals ₹9,000, the total salary comes out to ₹40,000.
Answer: 80%
Let the original income be 100. Then expenditure = 75 and savings = 25. New income = 120, expenditure remains 75, so new savings = 45. Increase in savings = 20, which is \(20/25\times100=80\%\).
Answer: 16 days
Prakash's rate is 1/20 work per day. Rahul's efficiency is 25% more, so his rate is 1.25 × 1/20 = 1/16 work per day. Hence Rahul completes the work in 16 days.
Answer: ₹ 2970
A 10% discount on ₹3000 gives ₹2700. Adding 10% GST on ₹2700 gives ₹2970, which is the net amount paid.
Answer: 40,000
If the population grows by 5% per year, then after two years it becomes multiplied by $1.05^2=1.1025$. So the population two years ago was $44100/1.1025=40000$.
Answer: 10:9
Let the first number be x. Then the second is 120% of x = 1.2x, and the third is 75% of 1.2x = 0.9x. So the ratio of the first to the third is x : 0.9x = 10 : 9.
Answer: 18.18%
Let the original value be 100. The correct value after a 10% increase is 110, while the mistaken value after a 10% decrease is 90. The shortfall is 20, and as a percentage of the correct value, \(20/110 \times 100 = 18.18\%\).
Q34. The difference between 25% of a number and 15% of the same number is 150. What is the number?
Answer: 1500
Let the number be \(x\). Then \(25\%\) of \(x\) minus \(15\%\) of \(x\) equals \(150\), so \(10\%\) of \(x=150\). Hence \(x=1500\).
Answer: Rs. 30,600
Successive depreciation means the value is reduced step by step. After 1st year: $50000\times0.85=42500$; after 2nd year: $42500\times0.90=38250$; after 3rd year: $38250\times0.80=30600$. Hence the final value is Rs. 30,600.
Answer: 50%
Initially, milk = 70% of 100 L = 70 L. After adding 40 L water, total mixture = 140 L while milk remains 70 L. So the new percentage of milk is \(\frac{70}{140}\times 100 = 50\%\).
Q37. A person spends \(\frac{3}{5}\) of his income and saves ₹4000. What is his income?
Answer: ₹ 10,000
If a person spends 3/5 of his income, he saves 2/5 of it. Given savings = ₹4000, so 2/5 of income = 4000. Therefore, income = 4000 × 5/2 = ₹10,000.
Answer: 30%
He spends 50% on food and household expenses and 20% on rent, so total spent is 70%. The remaining 30% is spent on miscellaneous items.
Answer: 2.67%
Let Y = 100, so X = 150. After increase, Y becomes 110 and X becomes 150(1 + k/100). Given X's new salary is 40% more than Y's new salary, X = 1.4 × 110 = 154. So 150(1 + k/100) = 154, giving k = 2.67% approximately.
Answer: 23.08%
If the original value is 100, after a 30% increase it becomes 130. Let the required decrease be \(x\%\); then \(130(1-x/100)=100\). Solving gives \(x=23.08\%\).
Answer: Rs. 16,500
On Rs. 25,000, a 30% discount gives Rs. 17,500. Since this amount is still above Rs. 15,000, an additional Rs. 1,000 is deducted. Final payment = Rs. 16,500.
Answer: -1%
If the original price is 100, after a 10% increase it becomes 110. A 10% decrease on 110 gives 99, which is 1 less than 100. So the net change is -1%.
Answer: 31.6
After a decrease of \(x\%\) and then an increase of \(x\%\), the net multiplier is \(1-\frac{x^2}{10000}\). Since the final price is 10% less, the multiplier is 0.9. Solving gives \(1-\frac{x^2}{10000}=0.9\), so \(x^2=1000\) and \(x\approx31.6\).
Q44. A number is increased by 25% and then decreased by 20%. What is the net change in the number?
Answer: No change
After a 25% increase, the number becomes 1.25 times the original. Then a 20% decrease makes it $1.25 \times 0.8 = 1$, so the final value is the same as the original.
Answer: 160
Red and green balls together are 50%, so blue balls are the remaining 50%. If 50% corresponds to 80 balls, then 100% corresponds to 160 balls.
Answer: 125
He attempted 75% of 200 = 150 questions, and 80% of those were correct, so \(150 \times 0.8 = 120\). Unattempted questions = 50, and 10% of them got grace marks, so \(50 \times 0.1 = 5\). Total right = \(120 + 5 = 125\).
Answer: 60
40% of 600 is 240. Then 25% of 240 is 60. So the required value is 60.
Answer: 20% decrease
If income is 100, expenses are 75 and savings are 25. After a 10% income increase, income becomes 110; after a 20% expense increase, expenses become 90. New savings = 110 - 90 = 20, which is a 20% decrease from 25.
Answer: $12\frac{36}{125}$ litres
In each operation, the fraction of milk left is $1-\frac{6}{30}=\frac{4}{5}$. After 4 repetitions, remaining milk = $30\left(\frac{4}{5}\right)^4 = 30\cdot\frac{256}{625} = 12.288$ litres, which is $12\frac{36}{125}$ litres.
Answer: 21.67%
If original income is 100, expenditure is 70 and savings are 30. New income becomes 110 and new expenditure becomes 73.5, so new savings are 36.5. The increase is 6.5 on 30, which is \(\frac{6.5}{30}\times 100 = 21.67\%\).