Spencer was 40 inches tall as a 4-year old which placed him in the top 10% of all children of similar age. the mean height for such children is 38 inches. based on this information, what is the standard deviation?

The 90th percentile is 1.2816 standard deviations from the mean. That tells you the standard deviation is ...

... (40 in - 38 in)/(1.2816) ≈ 1.56 in

The standard deviation for height for 4-year olds seems to be 1.56 inches.

3/5

step-by-step explanation:

double number line is not a standard concept, so it must have been defined in your textbook. assume top line is numerator.

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.