With mental math, you can perform equations quickly and efficiently. They also help you to develop your own strategies and solve more complex math equations. Hope this helps;)
No If it was 4 to 3 then yes but 4 can't be multiplied by anything to equal 9
The formula is d=C/π.
The diameter is 2 times the radius
The formula for the circumference using the radius is 2πr.
in order to do this backwards, we would have to do 16÷2÷π, but we're not looking for the radius.
Therefore, we take out the ÷2 part, which would be 16÷π
16 is the circumference
16÷π=d
d=C÷π
Triangle
1+1+5=7
7×4=28
28÷2=12
rectangle
12×5=60
whole shape
60+12=72in squared