Page 31 - 新思维数学活动用书8 样章

2 Expressions, formulae and equations

Practice

6 For each of these students
i Write an equation to represent what they say.
ii Solve your equation to find the value of x.
The first one is started for you.

a x + 1 = 20
My sister is 20 years old. 2
My Dad is x years old. x + 1 – 1 = 20 – 1
Half of my Dad’s age plus 1 is the 2
same as my sister’s age. x =
How old is my Dad? 2
x = × 2
x =
b
My brother is 9 years old.
My Mum is x years old.
One third of my Mum’s age minus
2 is the same as my brother’s age.
How old is my Mum?

c
My friend is 16 years old.
My Gran is x years old.
One quarter of my Gran’s age minus
8 is the same as my friend’s age.
How old is my Gran?

7 Work out the value of the algebraic unknown in each isosceles triangle.
All measurements are in centimetres. Show how you can check

your answers are correct.
a b
3a − 4 20 b
21 − 4
2

c d
c + 18 5c − 6 2(d + 1) d + 10

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