### Samuel Tok Keen Wei's answer to JT's Primary 6 Maths Measurement Singapore question.

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Draw a model to help you understand the question better. Since the price of a packet of biscuit is three times the price of a packet of snack, a packet of snack will be 1 unit and a packet of biscuit is 3 units.

1 water + 1 snack + 1 biscuit = \$5.40
1 water + 1 unit + 3 unit = \$ 5.40

And since water is \$3 less than biscuit, you can say that the price of a bottle of water + \$3 will be equal to the price of a biscuit. So you can add \$3 to both side of the equation.
(1 water +\$3.00) + 1 unit + 3 unit = \$5.40 + \$3.00
1 biscuit + 1 unit + 3 unit = \$8.40
3 unit + 1 unit + 3 unit = \$8.40
7 unit = \$8.40
1 unit = \$1.20

price of a bottle of water = 1 biscuit - \$3.00
price of a bottle of water = 3 unit - \$3.00
price of a bottle of water = (3 x \$1.20) - \$3.00
price of a bottle of water = \$3.60- \$3.00
price of a bottle of water = \$0.60

If you understand the basics of algebra, you can use the following methods below
Let the price of a packet of biscuit be X

1 water + 1 snack + 1 biscuit = \$5.40
(3X - \$3.00) + X + 3X = \$5.40
3X + X + 3X = \$5.40+\$3.00
7X = \$8.40
X=\$1.20

Price of water bottle = 3X -\$3.00
Price of water bottle = \$3.60 - \$3.00
Price of water bottle= \$0.60
Date Posted: 10 months ago