Explain how you could use mental math to find a 15% tip for a $26 restaurant bill.

1 answer:

3 0

10% of 26 is 2.60. Now, half of that is 1.30. Add both of them and you get 3.90. Same logic can work for a 20% tip, just double to 10%.

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In a certain year, when she was a high school senior, Idonna scored 671 on the mathematics part of the SAT. The distribution of

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Idonna's standardized score is 1.41.

Jonathan's standardized score is 0.55.

A.) Idonna's score is higher than Jonathan's

Step-by-step explanation:

Z-score:

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Idonna scored 671 on the mathematics part of the SAT. The distribution of SAT math scores in that year was Normal with mean 509 and standard deviation 115.

This means that her standardized score is Z when $X = 671, \mu = 509, \sigma = 115$ . So

$Z = \frac{X - \mu}{\sigma}$

$Z = \frac{671 - 509}{115}$

$Z = 1.41$

Idonna's standardized score is 1.41.

Jonathan took the ACT and scored 24 on the mathematics portion. ACT math scores for the same year were Normally distributed with mean 21.1 and standard deviation 5.3 .

This means that his standardized score is Z when $X = 24, \mu = 21.1, \sigma = 5.3$