KA-0113Unit conversion
3 points, difficulty 1 of 3Level 5–6about 45sA bag of flour holds 2.5 kg. 1750 g are used. How many grams are left?
Hints
Take them one at a time. The first gives nothing away.
1A nudge
Convert to grams before subtracting.
2The strategy
Put both amounts in the same unit first, and check the direction of the conversion by asking whether the number should get bigger or smaller. Then check the unit the answer is wanted in.
3The full solution
2.5 kg is 2500 g, and 2500 - 1750 = 750 g.
Solution— no shortcut on this one
Convert first: 1 kg is 1000 g, so 2.5 kg is 2500 g - bigger, as it should be. Then subtract in matching units: 2500 - 1750 = 750 g. The answer was asked for in grams, so 750 is the final answer, not 0.75. The transferable idea: convert, then calculate, then check the unit you were asked for.
Why this is on the test: Two unit traps in one question - the conversion and the answer's unit - and both are the kind that cost a mark on a question the student can do.