time yourselfMaths B (word problems)Fri 18 September1 / 4
Common denominators, in words
When you have an answer, always check whether it cancels
Name Date
The order① find the LCM of the denominators ② multiply top and bottom to match ③ add or subtract the numerators only ④ check whether it cancels
Calculate
45⁄12 ＋ 1⁄4
This one cancels.
Word problems — draw it before writing the calculation
5A ribbon is 7⁄8 m long. 1⁄3 m is used. How much is left?
6There is 2⁄5 L of juice and 3⁄10 L more. How much altogether?
7Work out 1⁄2 ＋ 1⁄3 ＋ 1⁄4.
Three fractions still need only one common denominator.
8Which is larger, 5⁄7 or 7⁄10 ? Use a common denominator.
9Someone wrote the answer to question 4 as 8⁄12. It is not wrong, but it is not how we write it. Why?
A little further
10A tank holds 3⁄4 L. 1⁄6 L is spilt, then 1⁄3 L is added. How much is in it now?
All three may go over one denominator at once.
11Put 4⁄9, 1⁄2 and 5⁄12 in order, smallest first.
12Write every fraction with denominator 12 that is bigger than 1⁄3 and smaller than 1⁄2.
"Every" means how many there are is part of the answer.
Extra · you may skip thisWork out 1⁄2 ＋ 1⁄4 ＋ 1⁄8 ＋ 1⁄16. Look at the answer and write what you notice.