The altitude of Death Valley, California, is 282 feet below sea level. A hot air balloon is launched from the bottom of Death Va
lley and rises at a rate of 10 feet per second. After 12 seconds, the balloon captain lowers the balloon 15 feet. What is the altitude of the hot air balloon after being lowered?
The factors of 9 are 3 and 3. (You need to multiply 3x3 to get 9.) The factors of 10 are 5 and 2. But, if you multiply 3 by 5, which gives you 15, and multiply the other 3 by 2, which gives you 6, and then add 6 to 15, you get 21.
