| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.19 |
| Score | 0% | 64% |
A machine in a factory has an error rate of 7 parts per 100. The machine normally runs 24 hours a day and produces 7 parts per hour. Yesterday the machine was shut down for 3 hours for maintenance.
How many error-free parts did the machine produce yesterday?
| 144 | |
| 136.7 | |
| 95.6 | |
| 96.6 |
The hourly error rate for this machine is the error rate in parts per 100 multiplied by the number of parts produced per hour:
\( \frac{7}{100} \) x 7 = \( \frac{7 \times 7}{100} \) = \( \frac{49}{100} \) = 0.49 errors per hour
So, in an average hour, the machine will produce 7 - 0.49 = 6.51 error free parts.
The machine ran for 24 - 3 = 21 hours yesterday so you would expect that 21 x 6.51 = 136.7 error free parts were produced yesterday.
What is \( \frac{4}{5} \) - \( \frac{8}{7} \)?
| 2 \( \frac{5}{35} \) | |
| -\(\frac{12}{35}\) | |
| 2 \( \frac{7}{16} \) | |
| 2 \( \frac{7}{35} \) |
To subtract these fractions, first find the lowest common multiple of their denominators. The first few multiples of 5 are [5, 10, 15, 20, 25, 30, 35, 40, 45, 50] and the first few multiples of 7 are [7, 14, 21, 28, 35, 42, 49, 56, 63, 70]. The first few multiples they share are [35, 70] making 35 the smallest multiple 5 and 7 share.
Next, convert the fractions so each denominator equals the lowest common multiple:
\( \frac{4 x 7}{5 x 7} \) - \( \frac{8 x 5}{7 x 5} \)
\( \frac{28}{35} \) - \( \frac{40}{35} \)
Now, because the fractions share a common denominator, you can subtract them:
\( \frac{28 - 40}{35} \) = \( \frac{-12}{35} \) = -\(\frac{12}{35}\)
A sports card collection contains football, baseball, and basketball cards. If the ratio of football to baseball cards is 5 to 2 and the ratio of baseball to basketball cards is 5 to 1, what is the ratio of football to basketball cards?
| 7:2 | |
| 25:2 | |
| 3:6 | |
| 1:1 |
The ratio of football cards to baseball cards is 5:2 and the ratio of baseball cards to basketball cards is 5:1. To solve this problem, we need the baseball card side of each ratio to be equal so we need to rewrite the ratios in terms of a common number of baseball cards. (Think of this like finding the common denominator when adding fractions.) The ratio of football to baseball cards can also be written as 25:10 and the ratio of baseball cards to basketball cards as 10:2. So, the ratio of football cards to basketball cards is football:baseball, baseball:basketball or 25:10, 10:2 which reduces to 25:2.
4! = ?
4 x 3 |
|
3 x 2 x 1 |
|
5 x 4 x 3 x 2 x 1 |
|
4 x 3 x 2 x 1 |
A factorial has the form n! and is the product of the integer (n) and all the positive integers below it. For example, 5! = 5 x 4 x 3 x 2 x 1 = 120.
Which of these numbers is a factor of 32?
| 1 | |
| 25 | |
| 24 | |
| 27 |
The factors of a number are all positive integers that divide evenly into the number. The factors of 32 are 1, 2, 4, 8, 16, 32.