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primary 6 | Maths
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How to solve? Stuck.
Date Posted: 4 years ago
Views: 2351
stickers
before
M: u
P: 4u
after
M: u+28
P: 4u+28
u+28 : 4u+28 = 5 : 6
6(u+28) = 5(4u+28)
u = 2
total stickers in pack = 10
before
M: u
P: 4u
after
M: u+28
P: 4u+28
u+28 : 4u+28 = 5 : 6
6(u+28) = 5(4u+28)
u = 2
total stickers in pack = 10
Thanks. How do u get 5:6?
Because Priscilla had 1/5 more than Mandy.
It's as good as saying Priscilla had 6 units, and Mandy had 5 units. So Priscilla has 1 unit more than Mandy. And this 1 unit is 1/5 of Mandy's 5 units.
Alternative method :
Notice that the difference in their number of stickers before and after obtaining 28 stickers each, is the same. This is so as they bought the same number of stickers.
Before:
Ratio of Mandy to Priscilla = 1 : 4
Difference = 4 units - 1 unit = 3 units
After :
Ratio of Mandy to Priscilla = 5 : 6
Difference = 6 units - 5 units = 1 unit
Since the difference is the same before and after, the number of units should be the same. So we make them the same.
Multiply by 3,
After :
Ratio of Mandy to Priscilla = 5 : 6 = 15 : 18
Difference = 1 unit x 3 = 3 units
So if we compare this with the ratio for 'before',
15 - 1 = 14
18 - 4 = 14
There is an increase of 14 units for each girl's number of stickers.
So 14 units = 28 stickers
1 unit = 28 stickers ÷ 14 = 2 stickers
Number of units at first = 4 + 1 = 5
So number of stickers in the packet
= 2 stickers x 5
= 10 stickers
It's as good as saying Priscilla had 6 units, and Mandy had 5 units. So Priscilla has 1 unit more than Mandy. And this 1 unit is 1/5 of Mandy's 5 units.
Alternative method :
Notice that the difference in their number of stickers before and after obtaining 28 stickers each, is the same. This is so as they bought the same number of stickers.
Before:
Ratio of Mandy to Priscilla = 1 : 4
Difference = 4 units - 1 unit = 3 units
After :
Ratio of Mandy to Priscilla = 5 : 6
Difference = 6 units - 5 units = 1 unit
Since the difference is the same before and after, the number of units should be the same. So we make them the same.
Multiply by 3,
After :
Ratio of Mandy to Priscilla = 5 : 6 = 15 : 18
Difference = 1 unit x 3 = 3 units
So if we compare this with the ratio for 'before',
15 - 1 = 14
18 - 4 = 14
There is an increase of 14 units for each girl's number of stickers.
So 14 units = 28 stickers
1 unit = 28 stickers ÷ 14 = 2 stickers
Number of units at first = 4 + 1 = 5
So number of stickers in the packet
= 2 stickers x 5
= 10 stickers
See 1 Answer
done
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Setup before-after ratios by adding in a “difference”. This difference must be the same as both persons added an equal number of stickers to their collection. So multiply the difference by a suitable number to make both ratios reflect the same number of units of difference. The difference between before and after for a person will therefore be the number of sweets added in.
Date Posted:
4 years ago
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