
Shortcut Trick
Required number = HCF of (1657 − 6) and (2037 − 5)
⇒ HCF of 1651 and 2032
Difference between the numbers = 2032 − 1651 = 381
The HCF must be a factor of their difference (381 = 3 × 127).
Since 1651 is not divisible by 3 (sum of digits is 13), the HCF is exactly 127.
∴ The correct answer is 127.

Alternate Method
Given:
Numbers = 1657 and 2037
Remainders = 6 and 5 respectively
Formula Used:
Greatest number = HCF of (First Number − First Remainder) and (Second Number − Second Remainder)
Calculations:
⇒ First number to be divided = 1657 − 6 = 1651
⇒ Second number to be divided = 2037 − 5 = 2032
⇒ We need to find the HCF of 1651 and 2032.
⇒ Prime factorization of 1651 = 13 × 127
⇒ Prime factorization of 2032 = 16 × 127 = 24 × 127
⇒ The common factor in both factorizations is 127.
⇒ Therefore, the HCF of 1651 and 2032 is 127.
∴ The correct answer is 127.

Additional Information
HCF of Numbers Leaving Same Remainder
To find the greatest number that divides x, y, and z leaving the same remainder in each case, calculate the HCF of |x − y|, |y − z|, and |z − x|.
HCF of Numbers Leaving Different Remainders
To find the greatest number that divides x, y, and z leaving remainders a, b, and c respectively, calculate the HCF of (x − a), (y − b), and (z − c).
LCM of Numbers Leaving Same Remainder
The smallest number which when divided by x, y, and z leaves the same remainder r in each case is given by LCM(x, y, z) + r.
Relation between HCF and LCM
For any two numbers a and b, the product of the numbers is equal to the product of their HCF and LCM: a × b = HCF(a, b) × LCM(a, b).