
By: Super (offline) Saturday, February 05 2011 @ 09:24 AM CST (Read 1815 times)



Super 
Hi,
Need help on the following maths question. Appreciate your assistance. Thanks in advance.
The ratio of $5notes to 20cents coins in Mr Tan's counter was 19:5. Mr Tan exchanged 15 of his $5notes for some 20cents coins. The ratio of the $5notes to 20cent coins then became 1:5. What was the total value of $5notes and 20cent coins at first?
Thanks.

Newbie
Registered: 08/12/09 Posts: 2





By: peterb5 (offline) Thursday, February 10 2011 @ 11:51 PM CST



peterb5 
It is quite a common type of question. You must remember that the total value of the money will not change. Thus you need to change the ratio to a ratio of value rather than a ratio of the number of notes and coins.
Before After
$5 : 20c $5 : 20c
number 19:5 1:5
value (converted to cents) 9500:100 500:100
simplify the ratio 95 : 1 5 : 1
as the total value must stay the same therefor find the lowest common multiple of 96 and 6 (96)
therefore we multiply the after ratio by 16
95 : 1 80 : 16
as you can see the $5 notes goes down by 15 units and 20c goes up by 15 units therefore
15 units > 15 x 5 = 75
1 unit > 75 divided by 15 = 5
96 units is 96 x 5 = 480

Newbie
Registered: 10/27/09 Posts: 1



