Page 49 - 新思维数学学生用书9 样章

2 Expressions and formulae

Exercise 2.6

1 a Write a formula for the number of seconds, S, in any number of minutes, M.
b Use your formula in part a to work out S when M = 15.
c Rearrange your formula in part a to make M the subject.

d Use your formula in part c to work out M when S = 1350.
2 a Use the formula F = ma to work out the value of
i F when m = 12 and a = 5
ii F when m = 26 and a = −3.
b Rearrange the formula F = ma to make m the subject.

Work out the value of m when F = 30 and a = 2.5.
c Rearrange the formula F = ma to make a the subject.
Work out the value of a when F = −14 and m = 8.

Think like a mathematician

3 Work with a partner to answer these questions.
a Copy and complete this table showing the number of

faces, edges and vertices of 3D shapes.

3D shape Number Number Number Tip
of faces of vertices of edges
cube Make a sketch
of each shape

cuboid to help you.

triangular prism

triangular-based
pyramid
square-based
pyramid
b Write a formula that connects the number of faces (F ), Tip

vertices (V ) and edges (E ).
Check your formula works for the shapes in the table. You studied
c Make V the subject of your formula. Euler’s formula

Work out V when in Stage 8.
i E = 10 and F = 6 ii E = 12 and F = 7.

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