A boy added all natural numbers from 1 to 10, however he added one number twice due to which the sum becomes 58. What is the number which he added twice?
A. 3
B. 4
C. 7
D. 8
Answer: Option A
Solution(By Examveda Team)
Sum of natural number from 1 to 10$$\eqalign{ & = \frac{{\left( n \right)\left( {n + 1} \right)}}{2}\,\,\,\,\,\,\,\left( {{\text{where }}n = 10} \right) \cr & = \frac{{10 \times 11}}{2} \cr & = 55 \cr} $$
Clearly, we can see the number which is added twice = 58 - 55 = 3
Related Questions on Number System
Three numbers are in ratio 1 : 2 : 3 and HCF is 12. The numbers are:
A. 12, 24, 36
B. 11, 22, 33
C. 12, 24, 32
D. 5, 10, 15
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