Chris walked the dog for 80 minutes or 1 hour and 20 minutes
Okay so lets call Leah "L" and her cousin "C". We know that L+C=36 ... we also know that Leah is twice her cousins age. Therefore, L=2 times C, or L=2C. This is because Leah's age is equivalent to twice as much as her cousin's.
Now that you know that L=2C, you can plug this back into the equation. This should make it so that's there's only one variable now!
L+C=36
(2C)+C=36 ... here we subbed in L=2C
3C=36 ... we add up the C's
C=12 ... we isolate for C by dividing both sides by 3
So her cousin's age is 12 years old. Leah's age is twice that. Thus, she's 24. If you add the two up: 12+24, you indeed get 36. Hope that helps :))
After 5 tests, her average was 88. To have a seven-test average of 90, the total must be:
Her average after 5 tests was 88. Her total score on the 5 tests is:
Subtract:
Find the average by dividing by 2:
Her average must be 95
One thing you could do is to expand either a factor of
or
, then expand the integrand. I'll do the first.
You have
which means the integral is equivalent to
Substitute
, so that
. This makes it so that the integral above can be rewritten in terms of
as
Now just use the power rule:
Back-substitute to get the antiderivative back in terms of
:
