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primary 5 | Maths
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Why is it is a decrease in unit? Why the 5 units add to 20 ribbons? Thank you.
Date Posted: 6 years ago
Views: 375
If she gives 5 of each type of ribbon away,
Blue ribbons left : 1 unit
Purple ribbons left : 7 units
So blue ribbons at first = 1 unit + 5
Purple ribbons at first = 7 units + 5
After buying 20 ribbons of each type,
Blue ribbons : 1 unit + 25
Purple ribbons : 7 unit + 25
Question says the blue ribbons is 1/2 of purple ribbons now. This also means number of purple ribbons is twice of blue ribbons.
So purple ribbons = 2 x (1 unit + 25 )
= 2 units + 50
2 units + 50 = 7 units + 25
On both sides, subtract 25 and 2 units
25 = 5 units
1 unit = 5
So 1 unit is 5 ribbons.
Total number of ribbons at first
= 1 unit + 5 + 7 units + 5
= 8 units + 10
= 8 x 5 + 10
= 40 + 10
= 50
Blue ribbons left : 1 unit
Purple ribbons left : 7 units
So blue ribbons at first = 1 unit + 5
Purple ribbons at first = 7 units + 5
After buying 20 ribbons of each type,
Blue ribbons : 1 unit + 25
Purple ribbons : 7 unit + 25
Question says the blue ribbons is 1/2 of purple ribbons now. This also means number of purple ribbons is twice of blue ribbons.
So purple ribbons = 2 x (1 unit + 25 )
= 2 units + 50
2 units + 50 = 7 units + 25
On both sides, subtract 25 and 2 units
25 = 5 units
1 unit = 5
So 1 unit is 5 ribbons.
Total number of ribbons at first
= 1 unit + 5 + 7 units + 5
= 8 units + 10
= 8 x 5 + 10
= 40 + 10
= 50
See 1 Answer
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Hope this helps
Date Posted:
6 years ago
Thank you so much.
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