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Q78·CSAT · Prelims 2022

Finding sets of consecutive integers whose sum equals their product

NumericalNumber PuzzlesFactual single● Medium

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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