Page 191 - NUMINO TG_6A
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Challenge Find Lengths of Body Parts
jOb ective Use proportions to compare measurements.

1. Textbook Instructions Challenge Find Lengths of Body Parts

1. Have students find the lengths of Thomas’ 1 . Thomas is 144 cm tall. Thomas is proportionally drawn on a piece of

other body parts. paper so that he is 12 cm tall. Use proportions to find the lengths of
Thomas’ body parts.

Example: 1a. Thomas’ head

Find the ratio of Thomas’ actual height to

his height on the page. a.
head
144 cm actual height to 12 cm on the arms

page: 144 actual = 144 = n 144 = n
12 picture 12 4 12 8

Find the unknown value. n = 96

The actual width of Thomas’ head. n = 48 4

Use the known, page value of Thomas’ 48 cm 96 cm

head to construct a second ratio, 4 .
n
8
Place the two ratios side by side as in 1

a proportion equation. hands

144 4 144 = n
12 n 12 1

Use cross products to solve for n. n = 12

144 4 12n, n 48

12 cm

106

2. Build Understanding

To help students recognize how proportions, and more specifically the cross product method, can be

applied to this problem, remind them of the basic formula that converts Thomas’ actual size to his size on

the page. 144
12

Note that this will always be the first ratio in any problem involving Thomas, because it sets the basic rules

of proportions for his body.

174 NUMINO Teacher s Guide
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