Rony, who is sixteen years old, is four times as old as his sister. How old will Rony be when he is twice as old as his sister?

1 answer

Now Rony is 16 years old

Sister is 16 / 4 = 4 years old

After x years Rony will be 16 + x

yeras old

Sister will be 4 + x years old

Now you must solve equation :

( 16 + x ) / ( 4 + x ) = 2 Multiply both sides by 4 + x

16 + x = 2 ( 4 + x )

16 + x = 8 + 2 x Subtract 8 to both sides

16 + x - 8 = 8 + 2 x - 8

8 + x = 2 x Subtract x to both sides

8 + x - x = 2 x - x

8 = x

x = 8

After 8 years Ronny will be 16 + 8 = 24 years old

Sister will be 4 + 8 = 12 years old

24 / 12 = 2