You can solve this one by adding their rates, but you have to invert the numbers they give you to find the rate. Rate is measured in something per unit of time, and "per" indicates division. So the rates are: 1/3 of an hour (Sally) and 1/6 of an hour (Steve). So add the rates: 1/3 + 1/6 = 1/2. (1/3 is 2/6, and 2/6 + 1/6 = 3/6). Since their combined rate is 1/2 of a room in one hour, it takes them two hours to paint the room.
This answer makes sense: It takes Sally three hours by herself; with Steve's help, she's faster, but not THAT much faster, because he's pretty slow. You can often spot-check word problem answers like this by giving it a common sense once-over. If we came up with four hours, that would clearly be wrong: it should take her LONGER if she's getting help.
Answer:
Step-by-step explanation:
Use the Pyhagorean theorem:
We have
Substitute:
<em>subtract 49 from both sides</em>
Answer:
0.16 m/s²
Step-by-step explanation:
Given:
Δx = 5600 m
v₀ = 0 m/s
v = 42 m/s
Find: a
v² = v₀² + 2aΔx
(42 m/s)² = (0 m/s)² + 2a (5600 m)
a = 0.16 m/s²
Surface area of the the rectangles:
8 * 5 + 8 * 4 + 8 * 3 = 96
Surface area of the two triangles:
Use bh/2 base time height over 2
(4 * 3)/2 = 6
There are 2 triangles, 2 * 6 = 12
12 + 96 = 108
