Multiple choice

A student got 55 marks in 5th test. As a result the average of his marks is increased by 5. The present average of his marks is

  1. 25

  2. 30

  3. 35

  4. 40
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the average of 4 tests be A. Total marks = 4A. After 5th test, (4A + 55) / 5 = A + 5. 4A + 55 = 5A + 25. A = 30. The present average is A + 5 = 35.

AI explanation

Let the previous average for 4 tests be A, making the previous total 4 times A. After scoring 55 in the 5th test, the new total is 4A plus 55, and the new average becomes A plus 5 across 5 tests. Setting the new total equal to 5 times (A + 5) gives the equation 4A + 55 = 5A + 25, which solves to A = 30. Since the present average is 5 more than the old average, the present average is 30 + 5 = 35. The present average of his marks is 35.

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