
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
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June 19th, 2018, 02:14 AM  #1 
Senior Member Joined: Aug 2014 From: India Posts: 341 Thanks: 1  How to do the problem?
The present age of A is equal to B's age ten years ago. Four years hence, the ratio of the ages of A and B will be 3:5. Find the present age of A. Solution: A = X B = Y X= Y  10 Y = X + 10 Four years hence X+ 4/ Y+ 4 = 3/5 Substitute Y in the equation: X + 4 / X + 14 = 3/5 X = 22/2 = 11 years. My doubt: They didn't mention B is older to A or vice versa. How to do the problem? 
June 19th, 2018, 02:41 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 19,865 Thanks: 1833 
Four years hence, "the ratio of the ages of A and B will be 3:5" means that B's age will exceed A's age by 2/3 of A's age, but we know that B is 10 years older than A, so A's age then will be 15 years and B's age will be 25 years (because 10 is 2/3 of 15). It follows that A's present age is 15 years  4 years, which is 11 years. 
June 19th, 2018, 01:23 PM  #3 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,441 Thanks: 946 
A li'l diagram always help: Code: A10 A A+4 B10 B B+4 <....................NOW.................> (A+4)/(B+4) = 3/5 [2] 