1. 5.8 Solving Ratio Problems Unit 5: Ratios

2.  In this movie poster, Ryan Reynolds is 8cm. Sandra Bullock is 6cm. If Ryan Reynolds is 1.8m tall in real life, how tall is Sandra Bullock?  The ratio Ryan’s height to Sandra’s height, is 8:6.

3.  Let h represent Sandra’s actual height, in cm.  Then, the ratio of the actual height of Ryan to the actual height of Sandra is 1.8 : h  1.8m = 180cm, so the ratio is 180:h  The two ratios are equivalent. Then… 180:h = 8:6

4.  To find the value of h, write a ratio equivalent to 8:6, with the first term 180.  Since 8 does not divide into 180 exactly, simply the ratio 8:6 first. 8:6 = 4:3  Write a ratio equivalent to 4:3 with the first term 180.  4:3 = 180:135 (multiply both sides by 45)

5.  So, 180:h = 180:135.  So, h = 135.  Sandra Bullocks actual height is 135cm or 1.35m.

6. Key Math Learnings:  Equal Ratios can be written as a proportion.  A proportion can be solved to find the value of an unknown term.

7. Find the value of each variable: a) 5:x = 40:56 b) 49:35 = 14:n