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Addition and Subtraction Quiz - CBSE Class 7 Mathematics

Free practice quiz: Addition and Subtraction (CBSE Class 7 Mathematics). 10 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This CBSE Class 7 Mathematics practice quiz has 10 multiple-choice questions on Addition and Subtraction, and 10 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

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Adding and subtracting like fractions

Like fractions have the same denominator.
Add or subtract only the numerators and keep the same denominator.

Sum of like fractions

\[\frac{a}{c}+\frac{b}{c}=\frac{a+b}{c}\]

Difference of like fractions

\[\frac{a}{c}-\frac{b}{c}=\frac{a-b}{c}\]

Common mistake: Adding the denominators too, for example writing a/c + b/c as (a+b)/(c+c). The denominator stays the same.

Unlike fractions: use the LCM

Unlike fractions have different denominators. First find the LCM of the denominators.
Change each fraction to an equivalent fraction with the LCM as its denominator, then add or subtract.
If one denominator divides the other, the bigger denominator is the LCM.

Equivalent fraction

\[\frac{a}{b}=\frac{a\times k}{b\times k},\quad k\neq 0\]

General sum

\[\frac{a}{b}+\frac{c}{d}=\frac{ad+bc}{bd}\]

General difference

\[\frac{a}{b}-\frac{c}{d}=\frac{ad-bc}{bd}\]

Common mistake: Multiplying only the denominator by k and forgetting the numerator. Both numerator and denominator must be multiplied by the same number.

Whole number minus a fraction

Write the whole number as a fraction with the same denominator as the other fraction.
Then subtract the numerators as with like fractions.

Whole number as a fraction

\[n=\frac{n\times b}{b}\]

Subtracting from a whole number

\[n-\frac{a}{b}=\frac{nb-a}{b}\]

Common mistake: Subtracting the numerator directly from the whole number, as if n - a/b were (n - a)/b.

Write the answer in lowest terms

After adding or subtracting, check if the numerator and denominator share a common factor.
Divide both by their HCF to get the simplest form.

Simplifying a fraction

\[\frac{a}{b}=\frac{a\div h}{b\div h},\quad h=\text{HCF}(a,b)\]

Common mistake: Leaving the answer unsimplified, or dividing only the numerator or only the denominator by the common factor.

Exam tips

Always check whether the denominators are the same before you start.
Use the LCM, not just any common multiple, to keep the numbers small.
In subtraction, your answer must be smaller than the first fraction. Use this to check your work.

Beta: made with AI and checked by a second AI. A teacher has not reviewed it yet.

Sample questions

What is 2/3 + 1/6?
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Answer: C. 5/6
To add 2/3 and 1/6, we need a common denominator of 6. Convert 2/3 to 4/6 and add 4/6 + 1/6 = 5/6.
Compute 1/3 + 1/4.
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Answer: B. 7/12
To add fractions, find a common denominator. Here, it is 12: 1/3 = 4/12, 1/4 = 3/12. Add: 4/12 + 3/12 = 7/12.
Calculate 2/5 + 3/10.
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Answer: A. 7/10
Convert to a common denominator of 10: 2/5 = 4/10. Add 4/10 + 3/10 = 7/10.
Given 3/7 + 4/21, find the sum.
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Answer: A. 13/21
Convert 3/7 to 9/21 (common denominator 21), then add 9/21 + 4/21 = 13/21.
Subtract 7/10 − 2/5.
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Answer: A. 3/10
Convert 2/5 to 4/10, and subtract 7/10 − 4/10 = 3/10.

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