A road that rises 1 ft for every 100 ft traveled to have a 1% grade. Portions of the Lewiston grade, near Lewiston,
Idaho, have a 6% grade. At what angle is this road inclined above the
horizontal?

The slope we find that in Idaho it rises 6 meters for every 100 traveled

given parameters

to find

The slope of a road or a ramp is the relationship between the amount that we rise to the horizontal distance traveled, the mathematical way to calculate is using the tangent

        tan θ = y / x

where θ is the angle, y is the vertical distance and x is the horizontal distance traveled

the slope is

       P% = θ * 100

It indicates that the 1% slope is 1 meter of elevation for every 100 meters traveled horizontally, thereforein with the slope we find Idaho it rises 6 meters for every 100 traveled

learn more about the slope here: link

in this case for Lewiston, the slope is 1%, that is, 1 meter of rise for every 100 me traveled

In the case of Idaho, the slope is 6%, that is, it rises 6 meters for every 100 meters traveled horizontally.

Explanation:

6% grade

=> Rises 6 feet for every 100 feet traveled

This would mean that tanx = 6/100.

=> x = tan^-1(6/100) = 3.4°. (1d.p.)

Hence the road is inclined at an angle of 3.4° above the horizontal.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form