When calculating simple interest, what must you do if you want to invest for months or weeks instead of years? a. simple interest only pays yearly, so you should find another investment. b. the simple interest calculation does not use those units, so you should just calculate as normal. c. the units have changed, so the interest formula switches to i·t=p·r. d. interest rates are annual, so you must convert the units into years

The correct answer is D.

Explanation:
Interest rates are given as an annual percentage rate. If you are investing for months or weeks, you will need to convert your units. You would divide the number of months by 12, since that would be the portion of a year it represents. For example, 3 months is 3/12 months, or 3/12 of a year. Similarly, if you were investing for weeks, you would divide by 52; if you want to invest for 6 weeks, that is 6/52 weeks, or 6/52 of a year.

It would be 15 m how i got the answer: (20x20) + b^2 = (25x25)400 + b^2 = 625625-400=225square that and get 15hope this : )