768 practice questions for CBSE Class 8 Mathematics, organised by NCERT chapter (7 chapters). Every question includes a written explanation. Pick a chapter below, or try the samples first.
Assertion (A): $3600$ is a perfect square. Reason (R): A number ending in two zeros is always a perfect square.
ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is true, but R is false
DA is false, but R is true
Show answer and explanation
Correct answer: C - A is true, but R is false
A is true because $60 \times 60 = 3600$. R is false: $200$ ends in two zeros but is not a square, since $14^2 = 196$ and $15^2 = 225$. So a true A sits with a false R, which rules out the first two choices and the last one.
Q2
easy
What is the value of $17^1$?
A$1$
B$17$
C$34$
D$171$
Show answer and explanation
Correct answer: B - $17$
An exponent of $1$ means the base appears exactly once as a factor, so $17^1 = 17$. The value $1$ mistakes the exponent for the answer, $171$ joins the digits, and $34$ doubles the base.
Q3
easy
A student writes: Step 1, $2(x + 5) = 2x + 10$; Step 2, $2x + 10 + 3x = 5x + 10$. Where is the mistake?
ABoth steps are wrong
BThere is no mistake; both steps are correct
CStep 1
DStep 2
Show answer and explanation
Correct answer: B - There is no mistake; both steps are correct
Step 1 multiplies both terms by $2$ correctly, and Step 2 combines the like terms $2x$ and $3x$ into $5x$ while leaving the constant alone. Checking with $x = 1$ gives $15$ at every stage, so the working is sound throughout.
Q4
medium
What is the quickest correct mental method for $7 \times 99$?
A$7 \times 90 + 9 = 639$
B$7 \times 100 - 1 = 699$
C$7 \times 100 - 7 = 693$
D$7 \times 100 + 7 = 707$
Show answer and explanation
Correct answer: C - $7 \times 100 - 7 = 693$
Since $99 = 100 - 1$, the product is $700 - 7 \times 1 = 693$. Subtracting only $1$ forgets to multiply the correction, $7 \times 90 + 9$ leaves the $9$ unmultiplied, and $7 \times 100 + 7$ adds where it should subtract.
Q5
hard
Consider these statements about whole numbers. (i) A zero written at the left end, as in $047$, changes the value of the number. (ii) A zero written inside, as in $407$, changes the value of the number. Which statement(s) are correct?
AOnly (ii)
BBoth (i) and (ii)
COnly (i)
DNeither (i) nor (ii)
Show answer and explanation
Correct answer: A - Only (ii)
A leading zero marks a place above the highest digit, and that place holds nothing, so $047$ is still $47$ and (i) is false. A zero inside pushes every digit on its left into a higher place, so $407$ is far larger than $47$ and (ii) is true. Only (ii) stands.
Q6
medium
Assertion (A): Walking at a steady $5\ \text{km/h}$ for $30$ minutes covers $2.5\ \text{km}$. Reason (R): Kilometres per hour is the unit normally used for the speed of vehicles on a highway.
ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is true, but R is false
DA is false, but R is true
Show answer and explanation
Correct answer: B - Both A and R are true, but R is not the correct explanation of A
Thirty minutes is half an hour, so the walker covers half of $5\ \text{km}$, which is $2.5\ \text{km}$, and A is true. R is a true statement about which unit is normally used for road speeds. Naming the usual unit does not explain the calculation in A, so R is not its reason.
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