Question

Jeremy's grandfather is four times as old as he is. If you add their ages together, you will get ninety. How old is Jeremy's grandfather? A. 18 B. 19 C. 70 D. 72

Answer 1

Answer: 72

Explanation:

Let Jeremy age be x

Granfather' age is 4x

x + 4x = 90

5x = 90

x = 90/5 = 18

Jeremy' age is 18

Granfather age is 4x = 4*18 = 72

Answer 2

`72`

Explanation:

Jeremy is
`x` years-old.

Jeremy's grandfather is
`4x` years-old.

Adding their ages together will get
`90`

`4x+x=90\\5x=90\\x=90 / 5\\x=18`

Jeremy's grandfather age would be:

`4x\\4(18)\\72`