An estimate always makes sense.
-- I have $10 in my pocket, this pump says $2.21 a gallon, and my car has been getting about 29 mpg. How many miles can I buy ?
-- I'm responsible for the reading two weeks from next Saturday. I'm about 1/3 of the way through learning 190 lines. How many lines must I average learning each day from now til then ?
-- I'm 32 miles from home and rush hour is srarting to build. My wife wants to know when I'll be there. What shall I tell her ?
X=9 Combine like terms, Move constant, then calculate.
I hope this helps you
42=1.42
42= 2.3.7
42= 6.7
I suspect 4/2 should actually be 4/3, since 4/2 = 2, while 4/3 would make V the volume of a sphere with radius r. But I'll stick with what's given:





In Mathematica, you can check this result via
D[4/2*Pi*r^3, r]