A student estimates: 'A bag of potatoes has a mass of about 2 grams.' What error did they make?
ANone — 2 grams is a reasonable estimate for a bag of potatoes
BThey confused grams and kilograms — a bag of potatoes has a mass of about 2 kilograms
CThey should have used liters instead of grams for food
DGrams can only be used for objects smaller than a coin
A gram is the mass of a single paperclip — a tiny amount. Two grams is about the mass of two paperclips. A bag of potatoes contains thousands of grams; a typical 2 kg bag = 2,000 g. This confusion between grams and kilograms is the most common error with metric mass. The fix is to anchor grams to a very light reference object (a paperclip) and kilograms to a heavier one (a textbook or a liter of water).
Question 2 Multiple Choice
How many grams are in 3 kilograms?
A300 grams
B30 grams
C3,000 grams
D30,000 grams
The prefix 'kilo-' always means 1,000 in the metric system, so 1 kg = 1,000 g. Therefore 3 kg = 3 × 1,000 = 3,000 g. Option A (300) confuses kilo- with hecto- (100). Keeping the conversion anchor '1 kg = 1,000 g' firmly in mind prevents this type of off-by-factor-of-10 error.
Question 3 True / False
A kilogram equals 100 grams, which is why it is heavier than a gram.
TTrue
FFalse
Answer: False
A kilogram equals 1,000 grams, not 100 grams. The prefix 'kilo-' means one thousand in all metric units (a kilometer is 1,000 meters; a kilogram is 1,000 grams). Confusing 1,000 with 100 is a common place-value slip that leads to large errors in mass calculations.
Question 4 True / False
When solving a mass word problem that involves adding two measurements, you should make sure both are expressed in the same unit before adding.
TTrue
FFalse
Answer: True
You cannot meaningfully add 500 g and 2 kg without first converting one to match the other (2 kg = 2,000 g, so the total is 2,500 g). Mixing units in arithmetic produces nonsense — just as you cannot add 3 feet and 2 meters without converting. Consistent units are the non-negotiable rule in all measurement work.
Question 5 Short Answer
Why is it important to choose the right unit — grams or kilograms — when estimating or measuring mass?
Think about your answer, then reveal below.
Model answer: Choosing the right unit keeps numbers manageable and avoids confusion. A strawberry's mass is sensibly expressed as 15 grams, not 0.015 kilograms. A person's mass is sensibly expressed as 60 kilograms, not 60,000 grams. Using the wrong unit produces numbers that are either absurdly large or absurdly small, making errors harder to catch and answers harder to interpret.
Unit choice also matters for communication: saying 'the box has a mass of 0.002 kilograms' is less clear than '2 grams.' Part of mathematical fluency is selecting the unit that makes the quantity easiest to reason about and communicate — and then converting as needed for calculations.