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Q78·CSAT · Prelims 2022

Finding sets of consecutive integers whose sum equals their product

NumericalNumber PuzzlesFactual singleMedium

Question

The sum of three consecutive integers is equal to their product. How many such possibilities are there?

Options

a

Only one

b

Only two

c

Only three

Answer
d

No such possibility is there

Explanation

Define three consecutive integers as (x-1), x, (x+1) to simplify the algebra.

Set up the algebraic equality: Sum = Product. (x-1) + x + (x+1) = (x-1)(x)(x+1) 3x = x(x² - 1)

Factor out the variable to expose all roots: x(x² - 1) - 3x = 0 x(x² - 1 - 3) = 0 x(x² - 4) = 0

This polynomial yields three distinct mathematical solutions for x:

Root 1: x = 0 \implies Sequence is \{-1, 0, 1\}. (Sum = 0, Product = 0).
Root 2: x² - 4 = 0 \implies x = 2 \implies Sequence is \{1, 2, 3\}. (Sum = 6, Product = 6).
Root 3: x² - 4 = 0 \implies x = -2 \implies Sequence is \{-3, -2, -1\}. (Sum = -6, Product = -6).

There are exactly three such possibilities.

Always anchor consecutive integer strings symmetrically around x (like x-1, x, x+1) to cancel out constants instantly during summation.

Answer: (c).

Question details

Year

2022

Paper

CSAT

Question

Q78

Section

Numerical Ability

Sub-topic

Number Puzzles

Type

Factual single

Difficulty

Medium

Source hint

Sum of three consecutive integers equal to product

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