Problem 1
A notebook costs 2.50 dollars and a ruler costs 5.90 dollars. How much do they cost altogether?
Answer: 8.40 dollars
- Line up the decimal points.
- 2.50 + 5.90 = 8.40.
- Money is a good decimal model because dollars and cents already use place value.
How to explain it: If your child starts lining up digits instead of decimal points, switch to cents first to make the structure clearer.
Problem 2
Leo had 5.90 dollars and spent 2.95 dollars. How much money did he have left?
Answer: 2.95 dollars
- This is subtraction because money is being spent.
- Line up the decimal points: 5.90 - 2.95.
- The amount left is 2.95 dollars.
How to explain it: Children often do better when they hear the money in words: dollars and cents, not just “decimal numbers.”
Problem 3
A rope is 7.75 metres long. Another rope is 8.25 metres long. What is their total length?
Answer: 16.00 metres
- Add the decimal lengths just like any place-value numbers.
- 7.75 + 8.25 = 16.00.
- Keep the unit metres in the answer.
How to explain it: Measurement contexts help children see that decimals are not abstract. They describe real lengths and amounts.
Problem 4
Which is greater: 4.4 or 5.8?
Answer: 5.8 is greater
- Compare the whole-number parts first.
- If needed, compare tenths after the decimal point.
- 5.8 is larger than 4.4.
How to explain it: A common mistake is thinking 3.8 is smaller than 3.24 because 24 is bigger than 8. Keep the place values lined up.
Problem 5
A bottle holds 2.50 litres of juice. 2.00 litres are poured out. How much juice remains?
Answer: 0.50 litres
- Start with 2.50 litres.
- Subtract the amount poured out: 2.50 - 2.00 = 0.50.
- Write 2.50, not 2.5, to keep the place values lined up.
How to explain it: Showing trailing zeros can be really helpful for children who still need to see each place value clearly.
Problem 6
A runner completed 1.35 km in the first lap and 1.45 km in the second lap. How far did the runner travel in total?
Answer: 2.80 km
- Add the decimal distances: 1.35 + 1.45.
- Hundredths: 5 + 5 = 10 hundredths, so regroup.
- The total is 2.80 km.
How to explain it: This is a nice example of regrouping inside decimal addition. Children often need to see that tenths and hundredths can regroup too.
Problem 7
A packet weighs 3.6 kg and another weighs 3.06 kg. Which one is heavier, and by how much?
Answer: 3.60 kg is heavier by 0.54 kg
- Rewrite 3.6 as 3.60 so both numbers have the same number of decimal places.
- Compare: 3.60 is greater than 3.06.
- Subtract: 3.60 - 3.06 = 0.54.
How to explain it: Rewriting 3.6 as 3.60 helps children understand that zeros can keep place value clear without changing the number.
Problem 8
A shop sells ribbon in pieces of 0.25 m. If a craft group buys 4 equal pieces, how much ribbon do they get?
Answer: 1.00 m
- This is repeated addition or multiplication: 0.25 × 4.
- Four groups of 0.25 make 1.00.
- So the craft group gets 1 metre of ribbon.
How to explain it: Quarter-dollar and quarter-metre examples help children see friendly decimal amounts more clearly.
Problem 9
A child saved 4.75 dollars in week one and 2.40 dollars in week two. How much was saved altogether?
Answer: 7.15 dollars
- Line up the decimals: 4.75 + 2.40.
- Add hundredths and tenths first, then whole dollars.
- The total saved is 7.15 dollars.
How to explain it: If children rush, they sometimes treat 4.75 like 475. Make them name the place values aloud.
Problem 10
A plant grew 0.85 cm on Monday, 0.65 cm on Tuesday, and 0.90 cm on Wednesday. How much did it grow in total?
Answer: 2.40 cm
- Add the first two days: 0.85 + 0.65 = 1.50.
- Add Wednesday: 1.50 + 0.90 = 2.40.
- The plant grew 2.40 cm in total.
How to explain it: Breaking a three-number decimal question into two smaller additions lowers stress and reduces place-value mistakes.