HOTS Mathematics Primary 4 Fractions

Nadia used 2/5 of a bag of flour to bake muffins and 1/4 of the same bag to bake cookies. The flour left over weighed 210 g more than the flour used for the cookies. How many grams of flour were in the bag originally?

A 2100 g
B 4200 g
C 700 g
D 840 g
Show Worked Solution

Worked Solution

Step 1: Find the total fraction of flour used for muffins and cookies. 2/5 + 1/4 = 8/20 + 5/20 = 13/20. Step 2: Find the fraction of flour left over. 1 − 13/20 = 20/20 − 13/20 = 7/20. Step 3: Find the difference between the leftover fraction and the cookies fraction. Cookies fraction = 1/4 = 5/20. 7/20 − 5/20 = 2/20 = 1/10. So 1/10 of the bag = 210 g (the leftover is 210 g MORE than the cookies portion). Step 4: Find the total mass of flour. 1/10 of total = 210 g Total = 210 × 10 = 2100 g. Answer: The bag of flour contained 2100 g originally.

Correct answer: 2100 g

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