For the three numbers 4, 6 and 10, work out HCF $x$ LCM and compare it with the product $4\times 6\times$ 10.
By how much does HCF $x$ LCM fall SHORT of the product?

HCF(4, 6, 10) = 2 and LCM(4, 6, 10) = $2^2\times 3\times 5=60$, so HCF $x$ LCM = 120. But $4\times 6\times$ 10 = 240, so the shortfall is 240 - 120 = 120. Answering 0 assumes the two-number rule HCF $x$ LCM = product also holds for three numbers - it does not.