Answer:
C. 3.5 × 120
Explanation:
The correct complete question should be with these options
a)14 x 30
b)7 x 60
c)3.5 x 120
d)None of these
Let's consider simple mental calculation of all the options one after the other
A. 14 x 30
= 14x3x10
=42x10=420 ( simple 3 steps)
B. 7x60
=42x10 =420 (simple 2 steps)
C. 3.5x120
=3x120+120x0.5
=360+60=420 (complex steps )
The correct answer is C because it involves multiple complex steps than the other options. It easier mentally break numbers up into smaller and easier pieces of integers than working with decimals.
