Grade 9 · Math · Unit 2 of 15
Rational Numbers
Fractions and decimals, positive and negative
What your child practises
Adding, subtracting, multiplying and dividing fractions and decimals that may be negative, converting between fractions and decimals, ordering rational numbers, and using BEDMAS.
Ontario Curriculum expectation: B3.1, B3.3, B3.4 · operations with positive and negative fractions, decimals and integers
How we explain it
Children can open this short lesson before they practise.
- A rational number can be written as a fraction.
- To add or subtract, use a common denominator.
- A negative times a negative is positive.
Example: −1/2 + 3/4 = ? Common denominator 4: −2/4 + 3/4. −2 + 3 = 1, so 1/4. Answer: 1/4
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
−2/3 + 2/5 = ?
- -16/15
- -1/5
- -4/15
- 4/15
- 0
Show answer
-4/15
Hint: Use the common denominator 15: -10/15 + 6/15 = -4/15, which is -4/15 in lowest terms.
Question 2
2/3 ÷ 5/4 = ?
- 3/5
- -8/15
- 8/15
- 15/8
- 1/2
Show answer
8/15
Hint: Multiply by the reciprocal: 2/3 × 4/5 = 8/15. A positive ÷ positive is positive. Lowest terms: 8/15.
Question 3
Calculate: 8.8 − 4.1 + 4.1 × 2
answer box
Show answer
12.9
Hint: Multiply first: 4.1 × 2 = 8.2. Then 8.8 − 4.1 = 4.7, and add: 12.9.
Question 4
−5.4 + 2.8 = ?
- 8.2
- -2.6
- -8.2
- 2.6
Show answer
-2.6
Hint: Different signs: subtract the sizes, 5.4 − 2.8 = 2.6, and keep the sign of the number farther from zero (−5.4). The answer is -2.6.
Question 5
Write 1/10 as a decimal.
answer box
Show answer
0.1
Hint: Divide the numerator by the denominator: 1 ÷ 10 = 0.1.
Question 6
What is the value of this expression? Remember BEDMAS.
8 + (-3) × 4 − 20 ÷ 5 = ?
answer box
Show answer
-8
Hint: Multiply and divide first: (−3) × 4 = -12 and 20 ÷ 5 = 4. Then 8 + (−12) − 4 = -8.