Question

The average of the 3 numbers is 20 if the sum of 2 of them is 42, what is the
third number?
a 18 b. 14 c. 28 d. 21​

Answer 1

Answer:

The answer will be 18 that is option (a).

Answer 2

Answer:

Concept:

         The "mean" is the average-calculating formula that is most frequently utilized. The mean is typically meant when the word "average" is used in a mathematical context, especially when no other context is provided. Divide the total by the number of numbers after adding up all the numbers.

Step-by-step explanation:

•    Since both terms are used to describe a set of numbers in mathematics, average and mean are frequently confused.

• By summing the collection of values and dividing by the number of quantities, the mean may be easily derived. Thus, this is the core definition of what mean is.

• To grasp the distinction between the average and mean, go to the tabular column below.

Given:

The average of the 3 numbers is 20.

The sum of 2 of them is 42.

To find:

The third number.

Solutions:

Let us take three numbers be a, b, c.

The average of the 3 numbers is 20.

so we can write,

a+ b+ c = 3 × 20

a+ b+ c = 60.....(1)

sum of two numbers is 42.

so we can write , a + b = 42  substitute the values in equation (1) we get

42 + c = 60

c = 60 - 42

c = 18

Hence the third number is 18.

The option a) 18  is correct.

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