AC Lim's answer to PurpleOlive's Primary 5 Maths Rate & Ratio Singapore question.
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If you like to solve using ratio ...
Before 1:3
R=1U
S= 3U
After new ratio 5:3
R= 1U + 105 = 5u
S= 3U- 9 = 3u
Divide S by 3
==> U -3 = u
==> U =u+3
Therefore,
New R
u +3 + 105 = 5u
108=4u
u = 108 / 4
u = 27
Old U = u +3 = 27+ 3 = 30......
Total Round = 30 +105 = 135.
Before 1:3
R=1U
S= 3U
After new ratio 5:3
R= 1U + 105 = 5u
S= 3U- 9 = 3u
Divide S by 3
==> U -3 = u
==> U =u+3
Therefore,
New R
u +3 + 105 = 5u
108=4u
u = 108 / 4
u = 27
Old U = u +3 = 27+ 3 = 30......
Total Round = 30 +105 = 135.
Date Posted:
4 years ago
Thank you. I'll try to understand the ratio method and explain to my child.
Look messy... I upload the hand written one...
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