IBPS SO Prelims Exam Model Paper 8

Given:
8 vehicles are in 1st row and there are 8 rows
Formula used:
Nth term of AP = a + (n – 1) d (a = 1st term , n = number of terms, d = common difference)
Sum of ‘n’ terms of AP =

n

2

× [2a + (n – 1) d]
Average = total number of vehicles/Number of rows
Calculation:
Using arithmetic progression formula,
a = 8, d = (-1) and N = 8
Total number of vehicles parked in 20 rows =

8

2

× [2 × 8 + (8 – 1) × (-1)]
= 4 × 9 = 36
∴ Required average = 36/8 = 4.5