Tao Nan School P5 SA2 2006 Math Q42

Alex has some red pens and blue pens in the ratio of 7:3. He has 20 more red pens than blue pens. What is the new ratio of the number of red pens to the number of blue pens after he has given away 5 blue pens?

Solution

Red : Blue
7 : 3
Difference between blue and red -----
4 units ----- 20
1 unit ----- 5

Number of pens
Red ----- 7 x 5 = 35
Blue ----- 3 x 5 = 15

After 5 blue pens given away
Red ----- 35
Blue ----- 15 – 5 = 10

New ratio
Red : Blue
35 : 10
7 : 2

Answer: The new ratio of red pens to blue pens is 7:2