J's answer to Luana's Primary 5 Maths Percentage Singapore question.
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$10 notes are 20% of total
Remainder : 100% - 20% = 80% of total
5 dollar notes are 40% of remainder.
40% is 40/100 and 40/100 = 2/5
So $5 notes are 2/5 of remainder.
2/5 of remainder = 2/5 x 80% of total = 32% of total
$2 notes = 100% - 32% - 20% = 48% of total
Ratio of $10 notes : $5 notes : $2 notes = 20 : 32 : 48
= 5 : 8 : 12
Based on the info above, we can group 12 $2 notes, 5 $10 notes and 8 $5 notes into 1 set. 5 + 8 + 12 = 25, so there are 25 notes in a set.
Value of notes in 1 set
= $2 x 12 + $10 x 5 + $5 x 8
= $24 + $50 + $40
= $114
Since there's a total of $1026, number of sets = $1026 ÷ $114 = 9
Total number of notes = 9 sets x 25 per set = 225
Remainder : 100% - 20% = 80% of total
5 dollar notes are 40% of remainder.
40% is 40/100 and 40/100 = 2/5
So $5 notes are 2/5 of remainder.
2/5 of remainder = 2/5 x 80% of total = 32% of total
$2 notes = 100% - 32% - 20% = 48% of total
Ratio of $10 notes : $5 notes : $2 notes = 20 : 32 : 48
= 5 : 8 : 12
Based on the info above, we can group 12 $2 notes, 5 $10 notes and 8 $5 notes into 1 set. 5 + 8 + 12 = 25, so there are 25 notes in a set.
Value of notes in 1 set
= $2 x 12 + $10 x 5 + $5 x 8
= $24 + $50 + $40
= $114
Since there's a total of $1026, number of sets = $1026 ÷ $114 = 9
Total number of notes = 9 sets x 25 per set = 225
Date Posted:
4 years ago
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