Page 14 - ACE YR IGCSE A TOP APPR' TO MATHS

3 A is proportional to B + 3B – 4.
2
A = 7 when B = 3.
Calculate the values of B when A= –2.

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4 The time, t minutes, for a water heater to boil some water is directly proportional to the mass of water,
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m kg.
When m = 1200 grams, t = 0.96 minutes.
Find the value of m when t = 5.

[2]

5 The time, t minutes, for a water heater to boil a fixed mass of water is inversely proportional to the
power supply, P watts, of the water heater.
When P = 220 watts, t = 0.25 minutes.
Find the value of t when P = 200.

[2]

6 The weight of a book is directly proportional to its number of pages.
Book A has 50 pages and a weight of 0.08 kg.
Book B has 720 pages, calculate its weight.

[2]

7 The amount of money Boey earns, m, is directly proportional to the number of hours she works, h.
If she works for 12.5 hours, she earns $131.25.
Find the amount of money she earns if she works 25 days in a month, 11 hours a day.

[2]

Chapter 1A Numbers 9

Chapter 1A.indd 9 15/03/2022 10:27 AM