sec. 4 ratios Flashcards
a) How do you write a ratio as a fraction?
b) How do reduce a ratio into its simplist form?
a) - Put the first number over the top of the second number e.g. 2:9 = 2/9
b) -Find what no. ÷s into both no.s
- Repeat this until it cannot be ÷ed further
* Note: a calculator will automatically cancell a fraction down to its simplist form when you press ‘=’
a) What do you do if a ratio conatains decimals?
b) what do you do if a ratio has diff. units?
e. g. Reduce the ratio 24mm:7.2cm to its simplist form
a) If a fraction contains a decimal x it by 10 or 100
b) Convert to the smaller unit
e. g. 24mm:7.2cm
24mm: 72mm
(÷24)
=1:3
a) How do do get ratios into the form 1:n or n:1?
b) Why is it useful to have the ratio in this form?
a) ÷ by the smaller no.
e. g. 3: 56
(÷3)
1: 56/3
b) It is useful in this form as it shows the ratio very clearly.
Scaling up ratio Q:
a) The ratio of sand and cement in mortar is 7:2. There are 21 buckets of sand. How many buckets of cement are needed?
a) 7 : 2
(x3)
21: 6
Part:Whole ratios
Miss M ha sboth tabby and ginger cats.The ratio of tabby cats to the total no. of cats is 3:5.
a) What fraction of miss M’s cats are tabby?
b) What is the ratio of tabby cats to ginger cats?
c) Miss M has 12 tabby cats. How many ginger does she have?
Proportional division Q:
J, M and G share £9100 in the ratio 2:4:7. How much does M get?
Changing Ratios Q:
There are 20 peacocks in sanctuary and the ratio of peackocks to pheasants is 4:9. 4 pheasants fly away. What is the new ratio?
…
a) Write thee in their simplist form:
1. 5:3 £1.26:14p 27mm:8.1cm
b) A rectangle has sides in the ratio 1:2. Calc. the length of the shorter side if the longer side is:
3cm 5.5cm 15.2m
c) ÷ the following by the ratios given
a) 1:2 9:1 7:2
b) 1.5cm 2.75cm 7.6m
c) 1hr 20m, 2hr 40m, 4hrs
Some strawberries I picked were either nibbled, mouldy or fineThe ratio was 2:3:10 respectively.
a) If 9 strawberries were mouldy how many:
i) were fine?
ii) were not fine?
b) What fraction of the total amount were fine?
a)
i) 30 fine
ii) 15 not fine
b) 30/45 =2/3
a) Reduce each into the form 1:n
8: 5 3:26 12:25
b) D has £17.50 in his pocket, and the ratio of D to S’s money is 5:4. D gives £4 to S. What is the new ratio of their amounts?
a) 1:0.625 1:8.6 1:2.083
b) D:S
5: 4
(x3.5)
17.50 : 14
(-4) (+4)
13.50 18
(x2)
27 : 36
(÷9)
3:4
The ratio of fiction to non-fiction books in a libary is 7:3.
60% of the fiction books are hardback, and 20% of the non-fiction books are hardback.
What % of all the books in the libary are hardback?
…
a) Changing ratios method?
e. g.
a)
