Can't get this wrong ! if the area of a circle measures 9π cm2, what is the circumference of the circle in terms of π? a) 3π cm b) 6π cm c) 9/4 π cm d) 9/2 π cm

A = π*r^2 . . . . . . . . . . . . formula for area
9 π cm^2 = π*r^2 . . . . . substitute the given information
9 cm^2 = r^2 . . . . . . . . divide by pi
3 cm = r . . . . . . . . . . . . . take the square root

C = 2π*r . . . . . . . . . . . . . formula for circumference
C = 2π(3 cm) . . . . . . . . substitute for r
C = 6π cm . . . . . . . . . . . matches selection B

1. 0.3 •4 is the same as 4 groups of 0.32. 7•0.8 is the same as 7 groups of 0.83. it increases by 0.5 every time, so 0.5x4 it increases by 0.9 every time, so 0.9x5. 0.9•12=10.86. 0.47•5=2.35i can finish the next ones in a separate post