1. Using fractions and percentages
[N3.1 Support Plenary]
1)What’s my number?
a) A quarter of it is five. b) 20% of it is three
c) Two-fifths of it is ten. d) 75% of it is thirty.
If you have time make up some more like these.
2) Carry on this fraction sequence for three more terms.
What is the rule?
Is the sequence increasing, deceasing or … ?
3) Without using a calculator, jot these fractions down in order of size.
Put the smallest first. How did you decide?
Preamble
These three activities are suitable for small groups. There are ample opportunities to
use mathematical vocabulary in the context of logical argument, for example sharing
thinking of how to answer (1) and (3). Questions such as those in (1) could be made up
by the pupils themselves – they require a firm grasp of fractions and percentages.
Although appearing to need a “reverse percentage treatment” the numbers are such
that a more informal approach is just as valid.
Possible content
Ordering fractions, simple percentages, some elements of informal trial and
improvement, pattern spotting.
Resources
None.
Solution/Notes
a) 20 b) 15 c) 25 d) 40
“Add 2 to the numerator and add 3 to the denominator” the sequence increases but the difference between terms gets smaller and smaller.
31/100 is larger than 31/110 (the former has smaller denominator) and 27/110 is smaller than 31/110 (the former has smaller numerator) 27/111 is smaller than 27/110 (the former has the larger denominator) So the order is 27/ / / /100
Original Material © Cambridge University Press 2010
Original Material © Cambridge University Press 2010