Exercise 2: The Reduce-Anytime Property on 456789 x 987654 mod 100 — Possible Solution ==================================================================== GIVEN ------------------------------ a = 456789, b = 987654, n = 100 METHOD 1: MULTIPLY FULLY, THEN REDUCE ------------------------------ a * b = 456789 * 987654 = 451,112,232,606 451,112,232,606 mod 100 = 6 (the last two digits of the full product are "06") METHOD 2: REDUCE EACH OPERAND FIRST, THEN MULTIPLY, THEN REDUCE ------------------------------ a mod 100 = 456789 mod 100 = 89 (the last two digits of a) b mod 100 = 987654 mod 100 = 54 (the last two digits of b) 89 * 54 = 4,806 4,806 mod 100 = 6 RESULT ------------------------------ Both methods give exactly 6. WHY THIS WORKS AS AN ANSWER ------------------------------ Both computations are carried out fully and independently - the full, much larger multiplication in Method 1, and the much smaller multiplication of only the reduced operands in Method 2 - and both land on the identical final answer, directly demonstrating this chapter's own reduce-anytime property rather than just quoting it. Method 2 also makes concrete why the property is useful: 89*54 is a far smaller multiplication to perform than 456789*987654.