CBSE Class 5 Mathematics Prime Numbers Worksheet

Q1 Fill in the blanks:
a) The number which is neither prime nor composite is ______________________ .
Answer: 1
In simple words: The number 1 has only one factor (itself), so it is neither prime nor composite.

Exam Tip: Remember that prime numbers have exactly 2 distinct factors (1 and the number itself), and composite numbers have more than 2 factors. Since 1 has only 1 factor, it belongs to neither category.

Q1 Fill in the blanks:
b) The smallest odd prime number is _________________________ .
Answer: 3
In simple words: The prime numbers are 2, 3, 5, 7, ... The number 2 is even, so the smallest odd prime is 3.

Exam Tip: 2 is the only even prime number. All other prime numbers are odd.

Q1 Fill in the blanks:
c) A prime number has ________________ factors.
Answer: exactly two (or 2)
In simple words: A prime number can only be divided evenly by 1 and by itself.

Exam Tip: Always specify that the factors are distinct and are specifically 1 and the number itself.

Q1 Fill in the blanks:
d) Prime numbers between 40 and 60 are ____________________________.
Answer: 41, 43, 47, 53, 59
In simple words: The numbers between 40 and 60 that have no factors other than 1 and themselves are 41, 43, 47, 53, and 59.

Q1 Fill in the blanks:
e) If a number is divisible by 6, it must be divisible by 2 and ______________ both.
Answer: 3
In simple words: Since 6 can be factored into prime numbers 2 and 3, any number divisible by 6 must be divisible by both 2 and 3.

Exam Tip: A number is divisible by 6 if it passes both the divisibility test for 2 (ends in an even digit) and the test for 3 (sum of digits is a multiple of 3).

Q1 Fill in the blanks:
f) All even numbers are divisible by _____________ .
Answer: 2
In simple words: By definition, any even number is a multiple of 2 and can be divided by 2 without a remainder.

Exam Tip: An even number always ends in 0, 2, 4, 6, or 8, making it always divisible by 2.

Q2 Fun while learn--- Let’s DECODE:
The buttons of a mobile phone have numbers with the letters of the English alphabets. Relating the letter with the number, solve the problems given alongside:
Now solve the following:
a) SCHOOL - BAG =
Answer:
Using the mobile keypad mapping:
S = 7, C = 2, H = 4, O = 6, O = 6, L = 5
So, SCHOOL = 724665
B = 2, A = 2, G = 4
So, BAG = 224
Now subtract:
\(724665 - 224 = 724441\)
In simple words: Convert each word into numbers using the mobile keypad, then subtract the second number from the first.

Exam Tip: Double-check the keypad mapping for each letter before performing arithmetic operations.

Q2 Fun while learn--- Let’s DECODE:
b) LAKHS + CRORES =
Answer:
Using the mobile keypad mapping:
L = 5, A = 2, K = 5, H = 4, S = 7
So, LAKHS = 52547
C = 2, R = 7, O = 6, R = 7, E = 3, S = 7
So, CRORES = 276737
Now add:
52547
+ 276737
= 329284
In simple words: Replace the letters with their respective mobile keypad digits and add the two numbers together.

Q2 Fun while learn--- Let’s DECODE:
c) PHONE x TV =
Answer:
Using the mobile keypad mapping:
P = 7, H = 4, O = 6, N = 6, E = 3
So, PHONE = 74663
T = 8, V = 8
So, TV = 88
Now multiply:
\(74663 \times 88 = 6570344\)
In simple words: Convert PHONE and TV into numbers using the keypad, then multiply them.

Exam Tip: Perform multi-digit multiplication carefully step-by-step to avoid calculation errors.

Q2 Fun while learn--- Let’s DECODE:
d) EVEN x ODD =
Answer:
Using the mobile keypad mapping:
E = 3, V = 8, E = 3, N = 6
So, EVEN = 3836
O = 6, D = 3, D = 3
So, ODD = 633
Now multiply:
\(3836 \times 633 = 2428188\)
In simple words: Translate the words EVEN and ODD into their number equivalents from the keypad and multiply them.

Exam Tip: Ensure all letter-to-number substitutions are cross-referenced correctly with the phone keypad diagram.