In the formula for the area of a circle, what gets multiplied by r?

Which triangle congruence postulate or theorem justifies my claim that the steps i made using construction paper and scissors produce an isosceles triangle? was it sss, sas, asa, aas, or hl?

Sally deposited money into a savings account paying 4% simple interest per year.the first year,she earned $75 in interest.how much interest will she earn during the following year?

How much is $1200 worth at the end of1 year,if the interest rate is 5.5% is compounded quarterly.