Question

if three quantities a,b,c be such that a:b=4:5 , b:c=15:16.find the ratio between a and c?

Answer 1

a:b=4:5

=> a/b =4/5
b=5a/4

Now  b/c=15/16
=> b=15c/16

=>5a/4=15c/16

=>a/c=3/4

=>a:c=3:4

Answer 2

a/b=n1/d1 b/c=n2/d2    
a:b=n1n2:d1d2
4*15:5*16
3:4