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## Monday, January 28, 2008

### MGS (Paya Lebar) Pri School P6 Math CA1 2006 (Q46)

Mrs Ng spent \$180 on pens and files. The ratio of the amount of money she spent on blue pens, red pens and files was 4 : 5 : 1. Blue pens were bought at 4 for \$1. The number of red pens she bought was 1/3 of the number of blue pens. The number of files was 3/8 of the number of red pens.

a) How much did she spend on blue pens?
b) How many red pens and files did she buy altogether?

Solution

Q(a) How much did she spend on blue pens?

10 units ----- \$180
1 unit ----- \$18
4 units ----- \$18 x 4 = \$72

Answer: She spent \$72 on blue pens.

Q(b) How many red pens and files did she buy altogether?

4 blue pens cost \$1.
Mrs Ng spent \$72 on blue pens.
\$1 ----- 4 blue pens
\$72 ----- 4 blue pens x 72 = 288 blue pens

Number of red pens bought was 1/3 the number of blue pens.
1/3 x 288 = 96 (red pens)

Number of files bought was 3/8 of number of red pens.
3/8 x 96 = 36 (files)

Total number of files and red pens -----
96 + 36 = 132

Answer: She bought a total of 132 files and red pens.