Matthew Soon's answer to Blursotong's Primary 6 Maths Data Analysis Singapore question.
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Trial and Error method:
At the start,
$2:$10
5 : 2
We try building a table of guesses to trial and error:
$2 | $10 | After exchange
5 , 2 》 15 , 0 (not possible to have ratio)
10 , 4 》 20 , 2 (the ratio is now 10:1)
15 , 6 》 25 , 4 (the ratio is now 25:4)
20 , 8 》 30 , 6 (the ratio is now 5:1) 《 correct
Tim had 8 $10 notes at first.
Algebra method:
Initial $2:$10 is 5x to 2x.
The exchange of notes and new ratio may be expressed as:
(5x+10)/(2x-2) = 5/1
10x-10 = 5x+10
5x = 20
x = 4
So Tim had 2(4) = 8 $10 notes at first.
At the start,
$2:$10
5 : 2
We try building a table of guesses to trial and error:
$2 | $10 | After exchange
5 , 2 》 15 , 0 (not possible to have ratio)
10 , 4 》 20 , 2 (the ratio is now 10:1)
15 , 6 》 25 , 4 (the ratio is now 25:4)
20 , 8 》 30 , 6 (the ratio is now 5:1) 《 correct
Tim had 8 $10 notes at first.
Algebra method:
Initial $2:$10 is 5x to 2x.
The exchange of notes and new ratio may be expressed as:
(5x+10)/(2x-2) = 5/1
10x-10 = 5x+10
5x = 20
x = 4
So Tim had 2(4) = 8 $10 notes at first.
Date Posted:
3 years ago
Appreciate your help. I roughly understand the trial and error method but I am totally lost with the algebra one, haha. But thank you again!
It's okay, at this stage you're more or less expected to be familiar with the trial and error method instead.
I can explain the algebra one a little bit more if you are interested to understand (posting a separate answer).
I can explain the algebra one a little bit more if you are interested to understand (posting a separate answer).
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