Page 19 - 新思维数学活动用书8 样章

2 Expressions, formulae and equations

9 Harsha uses the formula V = Ah to work out V when A = 6 and h = 12.
This is what she writes. 3

6 + 12
V =
3
18
=
3
= 6

a Explain the mistake she has made.

b Work out the correct answer.
( ab)
+
10 Use the formula A = × h to work out A when a = 5, b = 7 and h = 4.
2
11 Pedro uses this formula to work out the volume of a Tip
triangular-based pyramid:
Remember
V = bhl where: V is the volume that bhl means
6 b is the base b × h × l.
h is the height
l is the length.

Pedro compares two pyramids.
Pyramid A has a base width of 4 cm, base length of 3 cm and height of 16 cm.
Pyramid B has a base width of 6 cm, base length of 4 cm and height of 8 cm.
Which pyramid has the larger volume? Show your working.

12 Make x the subject of each formula.
Write if A, B or C is the correct answer.

a y = x − 8 A x = y − 8 B x = y + 8 C x = 8y

b y = kx A x = ky B x = y C x = k
k y

c y = x + w A x = y − w B x = y + w C x = w − y

x
d y = A x = y B x = r C x = ry
r r y

−
+
e y = 2x + t A x = yt B x = 2y + t C x = yt
2 2

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