Question

subtaract the sum of all prime numbers between 10 and 20 from the sum of all composite numbers between 10 and 20
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Answer 1

Solution!!

Composite numbers between 10 and 20 → 10, 12, 14, 15, 16, 18, 20

Sum of composite numbers between 10 and 20 = 10 + 12 + 14 + 15 + 16 + 18 + 20

= 105

Sum of composite numbers between 10 and 20 is 105.

Prime numbers between 10 and 20 → 11, 13, 17, 19

Sum of prime numbers between 10 and 20 = 11 + 13 + 17 + 19

= 60

Sum of prime numbers between 10 and 20 is 60.

We have to subtract the sum of the prime numbers between 10 and 20 from the sum of composite numbers between 10 and 20.

105 - 60 = 45

More information:-

Prime numbers → The numbers which are only divisible by itself and 1.

Composite numbers → The numbers which have more than 2 factors.

Answer 2

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The sum of all the prime numbers between 10 and 20 is 60. This dum is divisible by the single digits 1, 2, 3, 4, 5 and 6.

Sum of all = n(n+1)/2

= 20 x 21 /2

= 210;

Deduct Sum of 1+2+3+5+7+11+13+17+19=78

78 − 60 = 18

• I Hope it's Helpful My Friend.