| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 2.64 |
| Score | 0% | 53% |
A machine in a factory has an error rate of 2 parts per 100. The machine normally runs 24 hours a day and produces 10 parts per hour. Yesterday the machine was shut down for 4 hours for maintenance.
How many error-free parts did the machine produce yesterday?
| 72.8 | |
| 141.1 | |
| 196 | |
| 139.2 |
The hourly error rate for this machine is the error rate in parts per 100 multiplied by the number of parts produced per hour:
\( \frac{2}{100} \) x 10 = \( \frac{2 \times 10}{100} \) = \( \frac{20}{100} \) = 0.2 errors per hour
So, in an average hour, the machine will produce 10 - 0.2 = 9.8 error free parts.
The machine ran for 24 - 4 = 20 hours yesterday so you would expect that 20 x 9.8 = 196 error free parts were produced yesterday.
If a rectangle is twice as long as it is wide and has a perimeter of 6 meters, what is the area of the rectangle?
| 18 m2 | |
| 2 m2 | |
| 162 m2 | |
| 72 m2 |
The area of a rectangle is width (w) x height (h). In this problem we know that the rectangle is twice as long as it is wide so h = 2w. The perimeter of a rectangle is 2w + 2h and we know that the perimeter of this rectangle is 6 meters so the equation becomes: 2w + 2h = 6.
Putting these two equations together and solving for width (w):
2w + 2h = 6
w + h = \( \frac{6}{2} \)
w + h = 3
w = 3 - h
From the question we know that h = 2w so substituting 2w for h gives us:
w = 3 - 2w
3w = 3
w = \( \frac{3}{3} \)
w = 1
Since h = 2w that makes h = (2 x 1) = 2 and the area = h x w = 1 x 2 = 2 m2
What is \( 3 \)\( \sqrt{8} \) - \( 3 \)\( \sqrt{2} \)
| 9\( \sqrt{2} \) | |
| 9\( \sqrt{8} \) | |
| 3\( \sqrt{2} \) | |
| 0\( \sqrt{4} \) |
To subtract these radicals together their radicands must be the same:
3\( \sqrt{8} \) - 3\( \sqrt{2} \)
3\( \sqrt{4 \times 2} \) - 3\( \sqrt{2} \)
3\( \sqrt{2^2 \times 2} \) - 3\( \sqrt{2} \)
(3)(2)\( \sqrt{2} \) - 3\( \sqrt{2} \)
6\( \sqrt{2} \) - 3\( \sqrt{2} \)
Now that the radicands are identical, you can subtract them:
6\( \sqrt{2} \) - 3\( \sqrt{2} \)This property states taht the order of addition or multiplication does not mater. For example, 2 + 5 and 5 + 2 are equivalent.
distributive |
|
associative |
|
commutative |
|
PEDMAS |
The commutative property states that, when adding or multiplying numbers, the order in which they're added or multiplied does not matter. For example, 3 + 4 and 4 + 3 give the same result, as do 3 x 4 and 4 x 3.
What is \( \frac{2}{5} \) ÷ \( \frac{3}{5} \)?
| \(\frac{2}{15}\) | |
| \(\frac{8}{63}\) | |
| \(\frac{2}{3}\) | |
| \(\frac{1}{18}\) |
To divide fractions, invert the second fraction and then multiply:
\( \frac{2}{5} \) ÷ \( \frac{3}{5} \) = \( \frac{2}{5} \) x \( \frac{5}{3} \)
To multiply fractions, multiply the numerators together and then multiply the denominators together:
\( \frac{2}{5} \) x \( \frac{5}{3} \) = \( \frac{2 x 5}{5 x 3} \) = \( \frac{10}{15} \) = \(\frac{2}{3}\)