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time yourself

Maths B (word problems)Fri 11 September1 / 4

Common denominators and cancelling

Read the theory page first and this goes much faster

Name Date

First, the most common mistake

¹⁄₄ ＋ ¹⁄₆ ＝ ²⁄₁₀　This is wrong.

¹⁄₄ on its own is already bigger than ²⁄₁₀, so adding ¹⁄₆ cannot give something smaller.

Example

¹⁄₄ ＋ ¹⁄₆

① LCM of 4 and 6 → 12
② ¹⁄₄ ＝ ³⁄₁₂　¹⁄₆ ＝ ²⁄₁₂
③ ³⁄₁₂ ＋ ²⁄₁₂ ＝ ⁵⁄₁₂

Now you

1¹⁄₂ ＋ ¹⁄₃

2³⁄₄ ＋ ¹⁄₆

time yourself

Maths B (word problems)Fri 11 September2 / 4

Name Date

3⁵⁄₆ − ²⁄₉

4Simplify ²⁴⁄₃₆.

5¹⁄₄ ＋ ¹⁄₁₂　(simplify if you can)

6Which is larger, ²⁄₃ or ⁵⁄₈ ? Use a common denominator.

7A ribbon is ³⁄₄ m long. ¹⁄₆ m is used. How much is left?

Draw the picture before writing the calculation.

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Maths B (word problems)Fri 11 September3 / 4

Name Date

8Explain by meaning, not by method, why ¹⁄₂ ＋ ¹⁄₃ ＝ ²⁄₅ must be wrong.

This wants a sentence, not a number.

9With denominators 6 and 8 you could use 24 or 48. Why is 24 the usual choice?

10⁵⁄₈ ＋ ⁷⁄₁₂

The answer comes out bigger than 1.

time yourself

Maths B (word problems)Fri 11 September4 / 4

Name Date

11Put ³⁄₄, ⁵⁄₆ and ⁷⁄₉ in order, largest first.

12There is ²⁄₃ L of milk. ¹⁄₄ L is drunk in the morning and ¹⁄₆ L at night. How much is left?

Extra · you may skip this

Work out ¹⁄₂ ＋ ¹⁄₃ ＋ ¹⁄₆. Look at the answer and write down what you notice.