Hey guys,

I have a favor to ask of you. I need to be good at mental arithmetic for
an application test I gotta go through besides doing the GMAT. This has
nothing to do with the GMAT in the first place, but might be helpful nevertheless.
Please help me out.

The rules say, no writing utensils allowed. But still I have to solve problems like the following
in about 30 seconds in my head:

35% of 1720

5/2 x 7372 or
7/5 x 7260

I'm really having difficulties to solve this without writing it down.
Are there any strategies for solving this kind of questions?

Thanks in advance