Question

(a) Find the three consecutive natural numbers whose sum is 66.

(b) Find the three consecutive odd natural numbers whose sum is 39.

Answer 1

(a) 21, 22, 23

(b) 11, 13, 15

Explanation:

Natural numbers are the set of numbers 1, 2, 3... Not numbers that we think of as fractions or decimals or negative numbers.

Let x = the first number

Let x+ 1 = the second number

Let x+ 2 = the third number

x + x+ 1 + x + 2 = 66 Combine like terms

3x + 3 = 66 Subtract 3 from both sides

3x = 63 Divide both sides by 3

x = 21

Check:

21 + 22 + 23 = 66

Let x + the first number

Let x + 2 = the second number

Let x + 4 = the thirds number

x + x + 2 + x + 4 = 39 Combine like terms

3x + 6 = 39 Subtract 6 from both sides

3x = 33 Divide both sides by 3

x = 11

Check: 11 =+ 13 + 15 = 39