I have a doubt in this question

GRE Quant Problem Solving
1

I have a little doubt in this question 25 is ignored for PF because there is 50 whose PF have already 25 in 5^2 2^1 ?

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2

\operatorname{lcm} (a,b,c) = \operatorname{lcm}\left (\operatorname{lcm}(a,b), c \right)

So yes, you’re on the right track