How do I go about calculating these without using a calculator? (Mental Test)

I'm so stuck. I've read lots of books but would like it if a person would help me?
Thank you...

Attachment 26925Attachment 26926

1/4 of the marks come from the mental test ... OK, one-fourth of what? When you know what, multiply that by 1/4.

Does that help?

Suppose the total marks one may get in the exam is 16. How much (at most) one can get for the written paper? How much (at most) can you get for the mental test?

Let total marks be 100
then 75 marks written paper
and 25 marks of course work.

mental test marks = 75 × 1/4 = 18.75
% of 18.75/100 = 1875/10000
reduce to get in fraction form
= 75/400
= 3/16 part
or
direct calculations
1/4 of written = mental marks = 3/4 × 1/4 = 3/16
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