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 2s). 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 .