870 practice questions for CBSE Class 7 Mathematics, organised by NCERT chapter (8 chapters). Every question includes a written explanation. Pick a chapter below, or try the samples first.
Three numbers standing next to each other in the Virahanka sequence add up to $68$. What is the largest of the three?
A$55$
B$13$
C$21$
D$34$
Show answer and explanation
Correct answer: D - $34$
If the first two are $a$ and $b$, the third is $a + b$, so the total is $2(a + b) = 68$ and $a + b = 34$. The largest of the three is that third number, $34$, and the triple is $13$, $21$, $34$. The values $21$ and $13$ are the two smaller members, and $55$ is the number that follows the triple.
Q2
hard
One jar holds $\frac{4}{5}$ litre of oil and another holds $0.75$ litre. Which jar holds more, and by how much?
AThey hold the same amount
BThe first, by $0.5$ litre
CThe first, by $0.05$ litre
DThe second, by $0.05$ litre
Show answer and explanation
Correct answer: C - The first, by $0.05$ litre
Since $\frac{4}{5}=\frac{8}{10}=0.8$ litre, the first jar holds more, and $0.80-0.75=0.05$ litre. Choosing the second jar reverses the comparison, $0.5$ litre comes from subtracting the digits carelessly, and the two amounts are not equal.
Q3
hard
Which of these products is the smallest?
A$24 \times \frac{2}{3}$
B$24 \times \frac{5}{6}$
C$24 \times \frac{1}{2}$
D$24 \times \frac{3}{4}$
Show answer and explanation
Correct answer: C - $24 \times \frac{1}{2}$
The four products are $12$, $16$, $18$ and $20$, so the smallest comes from the smallest fraction, $\frac{1}{2}$. The other three fractions are each closer to $1$, and the nearer a proper fraction is to $1$, the more of the $24$ is kept.
Q4
medium
In the Virahanka sequence, an unknown number $x$ is followed by $21$ and then by $34$. Find $x$.
A$8$
B$12$
C$13$
D$55$
Show answer and explanation
Correct answer: C - $13$
The rule gives $x + 21 = 34$, so $x = 13$. The value $8$ lies one place earlier still, and $55$ is the number that comes after $34$. Subtracting $21$ from $33$ instead of $34$ gives $12$.
Q5
hard
A student writes $100 - (20 + 5) \times 2 = 150$. What went wrong, and what is the correct value?
ANothing went wrong, since $150$ is correct
BThe bracket was worked out too early; the correct value is $150$
CThe multiplication was done before the bracket; the correct value is $90$
DThe subtraction was done before the multiplication; the correct value is $50$
Show answer and explanation
Correct answer: D - The subtraction was done before the multiplication; the correct value is $50$
The bracket gives $25$, the product gives $50$, and $100 - 50 = 50$. The student calculated $(100 - 25) \times 2 = 150$, subtracting before multiplying. Working out the bracket first is exactly what the rules require, so that step was not the error.
Q6
easy
A student says that $\frac{1}{2}$ of $30$ is $60$. Why must this be wrong?
AHalf of a number is always a whole number
BHalf of a number is always smaller than the number
C$30$ is an even number
DHalving and doubling give the same answer
Show answer and explanation
Correct answer: B - Half of a number is always smaller than the number
Taking half keeps only part of the quantity, so the answer has to be less than $30$, and $60$ is more. Whether the answer is a whole number is beside the point, as is the fact that $30$ is even. Halving and doubling move in opposite directions, which is exactly the mistake made here.
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