Hannah is (3/7) as heavy as Irna and (3/4) as heavy as Jiahui. What is the ratio of Hannah's mass to the total mass of the 3 girls?

Answer 1

taking the ratios in reverse,
I/H = 7/3
J/H = 4/3
(I+J)/H = 11/3
I+J = 11/3 H
I+J+H = 14/3 H
so, H/(I+J+H) = 3/14

the simplest case is that Hannah weighs 3, Irna weighs 7, Jiahui weighs 4
The desired ratio is thus 3/(3+7+4) = 3/14