The answer is B:40 hours. You take 200 divided by 20 to get 10 (the amount of 20 page sections he needs to read) and then multiply 10 by 4 (the speed he reads).
160 square inches
if the block is cut after it’s been painted, two sides with the same measurements don’t have glitter on them. you find the area of the one rectangle and multiply it by 2 as follows:
A = length • width
A = 10 • 8 = 80
area that needs to be covered = 80 • 2 = 160 square inches
In order for two linear lines to be perpendicular, the product of their gradient must be -1.
Let's take y = x + b and y = -x + b
This is already in the form: y = mx + b, where m is 1 and -1 respectively.
Since the product of their gradient is -1, they are said to be perpendicular.
5. After 6 hours, the concentration is halved. After 12 hours, it will be quartered. If the original concentration is 200 nmol, a quarter is 50 nmol.
14. The population doubles after 3 hours, and a day is 24 hours. That means that the original population should be multiplied by
, or
. 3 million times
is 3 * 256 million, or 768 million.
15. The concentration is halved every 8 hours and the original concentration is 100 nmol. So now, how many times do you halve 100 to get to 12.5?
100/2 = 50, 50/2 = 25, 25/2 = 12.5. That's three times. 3 * 8 is 24 hours, or 1 day.