Question

A is 5 years older than b who is thrice as old as c.If the total of ages of a, b and c is 40, then how old is c ?

Answer 1

x= b

X+5= a

3(x+5)= 3x+15= c

x+x+5+3x+15= total age= 40

5x+20= 40

5x= 40-20= 20

x= 4= b

a= x+5= 9

c= 3x+15= 27

Therefore c is 27 years old.

Answer 2

Answer:

The age of A = 20 years.

The age of B = 15 years. The age of C = 5 years.

Step-by-step explanation:

Let x, y, z denote the respective ages of A, B, C.

Given, A is 5 years older than B.

∴ x = y + 5 ……………………………………..........................................(i)

Given, B is thrice as old as C.

∴ y = 3z …………………………............................................................(ii)

Given, total of ages of A, B and C is 40.

∴ x + y + z = 40 ……………………....................................................(iii)

To know how old is C, we have to determine z from equations (i), (ii), and (iii).

Substituting  y  in (i),

x = 3z + 5

Now substitute  x in equation (iii). We get

 3z + 5 + 3z + z = 40

→ 7z + 5 = 40

→ 7z = 40 - 5 = 35

→ z = 35/7

→  z = 5

∴ The age of C = 5 years.

∵ z = 5, from eqn. (ii) we will get,

 y = (3 x 5) = 15

∴ The age of B = 15 years.

and x = y + 5 = 15 + 5 = 20

∴ The age of A = 20 years.