Kendra says 6x65=390. estimate to check kendra’s answer

Hello!

There's more than one way in which to check this answer thru estimation. I'd find 6*60 and 6*70 separately, obtaining 360 and 420. It's obvious that Kendra's "390" is between 360 and 420, so it's likely that she's right.

6*65 does indeed equal 390.

In order to estimate the product of 6x65 in my head without writing anything down on paper or running home for my calculator, I close my eyes and I see something like this floating in space in front of me:

[6 · cos(2π)] · e⁰ · [60 · (1Hz/1cps)] = 360 but 65 is a little more than 60 so the product is probably a little more than 360 so 390 could be pretty close.

problem:

f(x) = - 2/3x + 5; f(5/2)

substitute 5/2 in for x:

f(5/2) = -2/3(5/2) + 5

simplify the right side:

f(5/2) = -5/3 + 5

f(5/2) = 10/3

f(5/2) = 10/3

i hope this !