Question 123

Out of four numbers, the average of the first three is 15 and that of the last three is 16. If the last number is 19, the first is

Solution

Given that the average of first 3 = 15 and average of last 3 is = 16

Using average = $$\frac{sum}{number of elements}$$

Sum of first 3 numbers = 15x3=45

Sum of last 3 numbers = 16x3=48

last number is given as=19

so sum of last two numbers = 48-19 = 29

so first number = 45-29 = 16

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