Ratio from My pals are here page 101

Question

Ms Sanjay had some red buttons and pink buttons in the ratio 1 : 3. She then bought 15 red and pink button each and the ratio became 2 : 5. How many pink buttons did she have at first.

Answer 1

red:pink=1:3

 

(1x+15)/(3x+15)=2/5

5(x+15)=2(3x+15)

5x+75=6x+30

75-30=6x-5x

x=45

45 red buttons originally and 3*45=135 pink buttons originally

check: (45+15)/(135+15)=60/150=6/15=2/5 or 2:5

Answer 2

beginning ratio: 1x : 3x

altered ratio: 1x + 15 : 3x + 15

proportion:

1x + 15 : 3x + 15 :: 2 : 5

5(x + 15) = 2(3x + 15)     product means/extremes

 

Can you solve for x and answer?