How many four-digit numbers are divisible by 11 and have a sum of digits of 10?

*Solution to yesterday’s problem:*

Let’s designate the square’s side length *a*. Then the area of the square is . To find the area of the triangle, we need to find its height. First we’ll draw the altitude to make two 30-60-90 right triangles (whose side lengths are *s*, , and 2*s*). The short side of each triangle is , so the vertical side is . Using the triangle area formula,

Now we can write our two areas as a ratio:

Canceling and multiplying both sides by four, we get the final answer .

### Like this:

Like Loading...

*Related*