Delhi Police Constable Exam Model Paper 8

Given:
A batsman scores 0 run in his ${19}^{\mathit{t}\mathit{h}}$ innings due to this his average is decreased by 5 runs
Concept:
When no runs scored in ${19}^{\mathit{t}\mathit{h}}$ innings, total runs decreases. And therefore Average also decreases
Calculation:
Let x be the average in 18thinnings
⇒ Total runs in 18 innings = 18x
∵ 0 run scored in ${19}^{\mathit{t}\mathit{h}}$ innings, total runs in 19 innings $=18\mathit{x}+0=18\mathit{x}$
Given that average decreases by 5 runs
∴ Average in ${19}^{\mathit{t}\mathit{h}}$ innings,
$18\frac{\mathit{x}}{19}=\mathit{x}-5$
⇒ $18\mathit{x}=19\mathit{x}-\left(19\times 5\right)$
∴ $\mathit{x}=95$
Average run in his ${18}^{\mathit{t}\mathit{h}}$ innings = 95