It will take 8 seconds for all of the dominoes to fall over.
This will be an exponential function. To find the growth rate, we can write out the terms of the sequence that goes along with it: 10, 20, 40, ...
"Growth rate" is the same as percent of increase or decrease. We find the amount of increase and divide by the original amount: 20-10 = 10 increase; 10/10 = 1.
The exponential function is of the form
f(x) = a*(1+r)ˣ, where a is the initial value (10), r is the growth rate (1), and x is the number of time periods. Using the variables given to us in the problem along with this information, we have:

Divide both sides by 10:

We will use logarithms to solve this:
If the initial time was 60 seconds and 18 seconds have passed,

There would be 42 seconds left.
3/5 x 7/7= 21/35
4/7x 5/5= 20/35
They both have a common denominator
Hey!
For 45-45-90 triangles you use you use the formula L(on the square root of)2
L represents the legs.
So you plug in
3(on the square root of)2 times (the square root of)2
You multiply the square roots to get
3(on the square root of)4
You simplify the square root of 4 to 2
So 3 times 2 = 6
So 6 is the answer
Hope this helped!