Page 298 - Math Smart - 7

Investigate!

Jaslyn measures the length of her foot and finds
that it is 21 cm long.
She then measures the length of her mother's foot
and finds that it is 24 cm long.

She decides to measure both their heights as well,
and records her measurements in a table like this:
Measurement Jaslyn jaslyn's Mother
Foot length (cm) 21 24
Height (cm) 133 152

Jaslyn says, "I must have big feet. My feet are nearly as long as my mother's!"
a) Calculate the ratio of the length of Jaslyn's foot to her height in simplest
form.
b) Calculate the ratio of the length of Jaslyn's mother's foot to her height in
simplest form.
c) What do you notice about the two ratios?
d) Does Jaslyn have bigger feet than normal for her height?

Xin mixes 3 ^ of red paint with 2 ^ of white paint.
Damien mixes 750 ml of red paint with 500 ml of white paint
Are the mixtures in proportion?

Solution
To compare the mixtures, we simplify the two ratios.

Xin's mixture is in the ratio of 3 : 2.
Damien's mixture Is in the ratio of 750 : 500 = (750 -r 250): (500 250)
o Journal Writing = 3:2.

They both mixed red and white paint in the ratio 3 : 2, so the mixtures are in
There were 15 girls and 10
proportion.
boys in Xin's maths class.
Xin said the ratio of the
Check My
number of girls to the
number of boys was 3 : 2. Understanding
Two new pupils, a girl
and a boy, joined the class
Sarah mixes 500 g flour with 200 g of sugar to make a cake.
halfway through the year.
Valerie mixes 360 g flour with 120 g of sugar to make another cake.
Xin says the ratio of the
a) For Sarah's cake mix, calculate the ratio of the amount of flour used
number of girls to the
to the amount of sugar used. Simplify your answer.
number of boys is still
b) For Valerie's cake mix, calculate the ratio of the amount of flour used
3:2.
to the amount of sugar used. Simplify your answer.
Is she correct? Why or why
c) Have the two girls mixed the flour and the sugar in the same
not?
proportion? Explain your answer.
UNIT 13 Ratio, Rate and Proportion