IBPS PO Quantitative Aptitude: Arrangement questions with solutions

Q1. In the given number "9657153428" the position of the first and second digits are interchanged, the third and fourth are interchanged, and so on. Then which digit will be 2nd to the left of the digit which is 5th from the left end?

1. 9
2. 7
3. 5
4. 6

Answer: 7

Original: 9(1),6(2),5(3),7(4),1(5),5(6),3(7),4(8),2(9),8(10). Swap pairs: pos(1,2)→6,9; pos(3,4)→7,5; pos(5,6)→5,1; pos(7,8)→4,3; pos(9,10)→8,2. New arrangement: 6,9,7,5,5,1,4,3,8,2. 5th from left = 5 (at position 5). 2nd to left of position 5 = position 3 = 7.

Q2. Series: 5 7 3 4 5 4 6 2 1 7 8 9 2 4 6 8 4 3 8 9 3 6 What is the sum of odd numbers placed between the numbers which are 4th from both ends?

1. 24
2. 25
3. 23
4. 22

Answer: 25

22-term series: 4th from left=pos 4=4; 4th from right=pos 19=8. Numbers between (pos 5 to 18): 5,4,6,2,1,7,8,9,2,4,6,8,4,3. Odd numbers: 5,1,7,9,3. Sum = 5+1+7+9+3 = 25.