What is the average (arithmetic mean) of all the multiples of ten from 10 to 190 inclusive?

A90
B95
C100
D105
E110

letter C: 100

Step-by-step explanation:

This problem can be configured as an arithmetic progression:

The first value is 10, the ratio is also 10 (the multiples of ten are 20, 30, 40, ...) and the number of terms is 19 (10, 20, 30, ... , 180, 190 -> total of 19 numbers).

So, we can use the following formula to calculate the sum of all these numbers:

Sn = n(a1 + an) /2

where Sn is the sum, n is the number of terms, a1 is the first term and an is the last one.

The result we want is the average of the sum, so we need to divide Sn by n:

Average = Sn/n = n(a1 + an) /2n = (a1 + an) /2 = (10+190)/2 = 200/2 = 100

The correct option is letter C.

c.   x=2.4cm

step-by-step explanation:

similar triangles are triangles which have the same shape but not the same size. this means their angle measures are equal but their side lengths are not instead they are proportional. to solve, we will set up a proportion and solve.

a proportion is two equal ratios set equal to each other. we form the ratios by finding corresponding sides (sides which match to each other on both triangles by their position). out ratios will be one side of the small triangle over the corresponding side on the big triangle as shown below:

.

to solve the proportion, we'll cross multiply by multiplying numerator with denominator across the equal sign.