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

Hope this is helpful, cheerio!