Question

The rainfall in Shillong for the first two days was in the ratio of 6 : 7. The average rainfall for the last four days was recorded to be 0.90 inch. The average rainfall of six days was 1.25 inch. Which of the following is/are correct?

A. Average rainfall on 2^nd day is 2.8 inch

B. Average rainfall on 1st day is 1.8 inch

C. Average rainfall on 2^nd day is 2.1 inch

D. Average rainfall on 1st day is 2.4 inch

1. Only A
2. A and D
3. B and C
4. None of these

Answer 1

Correct Answer - Option 3 : B and C

Given:

Ratio of rainfall for 1^st and 2^nd day = 6 ∶ 7

Average rainfall for the last four days = 0.90 inch

Average rainfall for all six days = 1.25 inch

Formula Used:

Average = Sum of values/Number of values

Calculation:

Let the rainfall on 1^st day be 6y and on 2^nd day be 7y

Sum of recorded rainfall for the last four days = Average rainfall for the last four days × Number of days

⇒ Sum of recorded rainfall for the last four days = 0.90 × 4

⇒ Sum of recorded rainfall for the last four days = 3.60

Sum of recorded rainfall for all six days = Average rainfall for all six days × Number of days

⇒ Sum of recorded rainfall for all six days = 1.25 × 6

⇒ Sum of recorded rainfall for all six days = 7.50

⇒ 6y + 7y + 3.60 = 7.50

⇒ 13y = 3.9

⇒ y = 0.3

The rainfall on 1^st day = 6y

⇒ 6 × 0.3

⇒ 1.8

The rainfall on 2^nd day = 7y

⇒ 7 × 0.3

⇒ 2.1

Average rainfall on 1st day is 1.8 inch and average rainfall on 2^nd day is 2.1 inch.

∴ B and C are correct