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Friday, November 17 2017 @ 10:32 PM CST
 Forum Index >  Test Paper Related >  Primary 6 Matters
 P6 Math Fraction
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By: Xrong (offline)  Friday, September 06 2013 @ 11:42 PM CDT (Read 797 times)  
Xrong

Please kind help below quention, thank you.

Q1)
In a piggybank, the number of ten-cent coins was 2/5 of number of twenty-cent coins.
Lily took out 10 twenty-cent coins from the piggybank and
exchanged them all for ten-cent coins.
She then put the new ten-cent coins into the piggybank.
The number of twenty-cent coins then became 5/8 of the number of ten-cents.
How much money was there in the piggybank?

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By: jo sarah (offline)  Saturday, September 07 2013 @ 04:24 AM CDT  
jo sarah

Q1)
In a piggybank, the number of ten-cent coins was 2/5 of number of twenty-cent coins.
Lily took out 10 twenty-cent coins from the piggybank and
exchanged them all for ten-cent coins.
She then put the new ten-cent coins into the piggybank.
The number of twenty-cent coins then became 5/8 of the number of ten-cents.
How much money was there in the piggybank?

Solution:
.....................10 cts coins...........20 cts coins
before:.............2u..............................5u....................[u: unit]
change:..........+20............................-10
in end:.............8p..............................5p....................[p: part]

So, for the 10cts coins: 2u + 20 = 8p
then,............................. 1u + 10 = 4p; that is, 1u = 4p - 10
so that,...............................5u = 20p - 50
for the 20cts coins:........5u - 10 = 5p
therefore,...................20p - 50 - 10 = 5p
thus,.............................15p = 60
and so, ..........................1p = 4

Total sum of money in piggy = (8 x 4 x $0.10) + (5 x 4 x $0.20)
..............................................= $7.20

Check:
so, 1u = 4p - 10 = 6
and in beginning, there are 12 10cts coins and 30 20cts coins, which give same total;
as well, 12 + 20 = 32; and 30 - 10 = 20; which gives the ratio of 8 : 5 Laughing Out Loud

Hope this is helpful, cheerio! Big Grin

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