Question

Rs 720 is divided between X and Y the ratio 4 by 5 how many rupees will each get

Answer 1

4x+5x=720
9x=yep
x=720/9
x=80

Answer 2

Share of x: share of y=4:5⇒4a:5a where a is the common divisor
total share= 4a+5a=9a but
total share =720rs
9a=720
a=80
share of x =4a-4*80=320rs
share of y=5a*80=400rs

Shortcut method
share of x=share of ratio of x*total amount/total of ratio
=4*720/(4+5)
=4*720/9=4*80=320rs
share of y=5*720/9=5*80=400rs

this is your answer