What's the procedure to "express these fractions as 30 seconds"?

1/4 , 3/4 , 11/8 , 7/16 , 21/16 , 197/16 , 21/8

I assume you mean 32nds. Look at the bottom number 1/? How much do you need to multiply it to get 32? Then multiply each top # by the same amount. What you have posted are reduced fractions, all divide into 32.

4 , 8 , 16 are denominators..

4 , 8 , 16 are denominators..
Correct. All are denominators can be multiplied by various numbers to make 32 ("thirty-seconds") as a denominator. When you multiply the denominator by a number, you must multiple the numerator by the same number.

Should I multiply den, num by "30"? Or multiply only the den to get 32 as a first step,then multiply the num by the same number?
Thanks

Should I multiply den, num by "30"?
NO! Why would you do that?

Or multiply only the den to get 32 as a first step,then multiply the num by the same number?
Thanks
Yes. Now show me!

Will you write me the procedure please?

Thank you

Will you write me the procedure please?

Thank you
1/2 = 16/32

I multiplied both top (numerator) and bottom (denominator) by 16 so the denominator will be 32.

OP is confused about 32nds and 30 seconds. PM indicated such.

Ayharok. Your PM regarding the questions in the book indicates, at least to me, that the book has errata. "30 seconds" has no bearing in fractions, it should be 32nds. If we were talking circular items, seconds may be applicable. Follow what Wondergirl and I have posted.