Question : A boy added all-natural numbers from 1 to 20. However, he added one number twice, due to which the sum became 215. What is the number which he added twice?
Option 1: 5
Option 2: 7
Option 3: 11
Option 4: 15
Correct Answer: 5
Solution : Let the number added twice be $x$. The sum of all $n$ natural numbers = $\frac{n(n + 1)}{2}$ The sum of all natural numbers from 1 to 20 = $\frac{20(20 + 1)}{2}$ = $\frac{21 × 20}{2}$ = 210 According to the question, ⇒ 210 + $x$ = 215 ⇒ $x$ = 5 Hence, the correct answer is 5.
Application | Eligibility | Selection Process | Result | Cutoff | Admit Card | Preparation Tips
Question : A boy added all natural numbers from 1 to 12, but he added one number twice, due to which the sum became 80. What is the number that he added twice?
Option 1: 3
Option 2: 2
Option 3: 7
Option 4: 8
Question : Arrange the given ratios in descending order 15 : 7, 5 : 11, and 21 : 77.
Option 1: 21 : 77 > 5 : 11 > 15 : 7
Option 2: 15 : 7 > 5 : 11 > 21 : 77
Option 3: 15 : 7 > 21 : 77 > 5 : 11
Option 4: 5 : 11 > 15 : 7 > 21 : 77
Question : If the sum of two numbers is 60 and their HCF and LCM are 5 and 60, respectively, then the sum of the reciprocals of the numbers will be:
Option 1: $\frac{1}{11}$
Option 2: $\frac{1}{6}$
Option 3: $\frac{1}{4}$
Option 4: $\frac{1}{5}$
Question : Directions: When a number is added to its next number and another number that is four times its next number, the sum of these three numbers is 95. Find the number.
Option 1: 16
Option 2: 14
Option 3: 17
Question : There are three numbers where the first number is twice the second, and the second is thrice the third number. If the average of the three numbers is 20, what is the sum of the largest and smallest numbers?
Option 1: 24
Option 2: 42
Option 3: 54
Option 4: 60
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile