Central Tendency & DispersionMTP June 22Question 2908 of 473
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A batsman in his 20th\displaystyle 20^{th} innings makes a score of 120\displaystyle 120 and thereby increases his average by 5\displaystyle 5. What is his average after 20th\displaystyle 20^{th} innings?

Options

A60
B55
C25
D70
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Correct Answer

✅ Option c — 25

All Options:

  • A60
  • B55
  • C25
  • D70

Detailed Solution & Explanation

**Step 1: Set up the equation.** Let the average after 19 innings =a\displaystyle = a. Then total score after 19 innings =19a\displaystyle = 19a. After 20th innings, average increases by 5: New average=a+5\text{New average} = a + 5 19a+12020=a+5\frac{19a + 120}{20} = a + 5 **Step 2: Solve.** 19a+120=20a+10019a + 120 = 20a + 100 120−100=20a−19a120 - 100 = 20a - 19a a=20a = 20 **Step 3: Compute average after 20th innings.** Average after 20th=a+5=20+5=25\text{Average after 20th} = a + 5 = 20 + 5 = 25 **Note:** The computed average after 20th innings is **25** (Option C), not 55 (Option B). Wait — let me reconsider. Perhaps the average increases BY 5 from 19 innings to 20, meaning each innings contributes. Let me recheck. Actually, the standard approach: Let average after 20 innings =A\displaystyle = A. Average after 19 innings =A−5\displaystyle = A - 5. 19(A−5)+120=20A19(A-5) + 120 = 20A 19A−95+120=20A19A - 95 + 120 = 20A 25=A25 = A So average after 20th innings =25\displaystyle = 25 (Option C). Hence, **Option C** is the correct answer.

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