Proportion
Answers are for parents and teachers.
1
Write 42 : 56 in simplest form.
3 : 4 (divide both terms by 14).
2
Is 7 : 9 = 21 : 27 a proportion? Show the cross products.
Yes. 7 × 27 = 189 and 9 × 21 = 189.
3
Find x: 9 : 15 = x : 20.
15 × x = 9 × 20 = 180, so x = 12.
4
6 pens cost 45 LE. How much do 10 pens cost at the same rate?
6 : 45 = 10 : x, so x = 45 × 10 ÷ 6 = 75. They cost 75 LE.
5
A car travels 60 km in 1 hour, 120 km in 2 hours and 170 km in 3 hours. Are distance and time proportional? Explain.
No. 60 ÷ 1 = 60 and 120 ÷ 2 = 60, but 170 ÷ 3 is about 56.7, so the ratio changes.