Shortcut Trick
Find the differences between the given numbers: (50 − 38), (74 − 50), and (98 − 74).
Differences are 12, 24, and 24.
The HCF (Highest Common Factor) of 12, 24, and 24 is 12.
Thus, 12 is the largest number that leaves the same remainder (2) in each case.
∴ The correct answer is 12.
Alternate Method
Given: The numbers are 38, 50, 74, and 98.
Formula: To find the largest number that divides several numbers leaving the same remainder, find the HCF of the absolute differences between the numbers.
⇒ First difference = |50 − 38| = 12
⇒ Second difference = |74 − 50| = 24
⇒ Third difference = |98 − 74| = 24
⇒ Required Number = HCF of (12, 24, 24)
⇒ Factors of 12 = 1, 2, 3, 4, 6, 12
⇒ Factors of 24 = 1, 2, 3, 4, 6, 8, 12, 24
⇒ Common Factors = 1, 2, 3, 4, 6, 12
⇒ Highest Common Factor (HCF) = 12
∴ The correct answer is 12.
Additional Information
HCF with Specific Remainders
To find the largest number that divides A, B, and C leaving remainders x, y, and z respectively, find the HCF of (A − x), (B − y), and (C − z).
LCM with Same Remainder
The smallest number which when divided by x, y, and z leaves the same remainder 'r' in each case is [LCM(x, y, z) + r].
HCF Property
The HCF of a set of numbers always divides the difference between any two numbers in that set.