Page 32 - 新思维数学活动用书9 样章

2.6 Deriving and using formulae

2.6 Deriving and using formulae

Exercise 2.6 Key words

changing the
Focus subject
1 You already know a lot of mathematical formulae. subject of a

Match each rectangular card with the correct oval card. formula

A Area of a triangle B Volume of a cuboid

C Area of a parallelogram D Circumference of a circle

E Area of a trapezium F Area of a circle

=
i A = π r 2 ii A bh iii C = π d

1
iv V = lbh v A = 1 bh vi A = ( a + b h
)
2 2
2 a Work out the number of hours in
i 1 day ii 2 days
iii 3 days iv d days.
b The formula to work out the number of hours (H) in d days

is H = 24d. Tip
Copy and complete the working to find the number of hours Substitute d = 10
in 10 days. into the formula.
H = 24d = 24 × d = 24 × 10 =

3 a Work out the number of days in
i 1 week ii 2 weeks
iii 3 weeks iv w weeks.
b Copy and complete the formula to work out the number of days (D) in w weeks: D = ……
Use your formula to find the number of days in 8 weeks.

4 a Work out the total number of days in
i 1 week and 2 days ii 3 weeks and 4 days
iii w weeks and d days.

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