Question 981211
Two numbers are such that the ratio between them is 3:5. If each is increased by 10, the ratio b/w the new numbers so formed as 5:7. Find the original number?
<pre>Let multiplicative factor be x
Then numbers are: 3x and 5x
We then get: {{{(3x + 10)/(5x + 10) = 5/7}}}
7(3x + 10) = 5(5x + 10) -------- Cross-multiplying
21x + 70 = 25x + 50
21x - 25x = 50 - 70 
- 4x = - 20
{{{x = (- 20)/(- 4)}}}, or 5
Smaller original number:  3(5), or {{{highlight_green(15)}}}
Larger original number:   5(5), or {{{highlight_green(25)}}}