Question

1/4 of a rod was painted red. 2/5 was painted orange and 2/7 of the remainder was painted yellow. The yellow section was 20cm long how long was the rod

Answer 1

Answer: 200cm long

Explanation:

Let the length of the rod be x

red = 1/4 of the rod , which means 1/4 of x

orange = 2/5 of x

The remainder = x - (
`(x)/(4)` +
`(2x)/(5)`)

= x - (
`(13x)/(20)`)

=
`(7x)/(20)`

yellow = 2/7 of the remainder , that is

yellow = 2/7 of
`(7x)/(20)`

yellow =
`(x)/(10)`

and it was given that the yellow section was 20cm long , that is

`(x)/(10)` = 20cm

x = 20 x10

x = 200

Therefore the rod was 200cm long