Answer:
a. -9 feet b. We have that the hole is 9 feet deep
Step-by-step explanation:
a. Let's take the ground level to be our zero point. At first, on the first day, they dug a hole of 3 feet. This is represented by -3 feet since it is below ground level. On the second day, they dug two more feet, this is represented by -2 feet. On the third day, they dug four more feet, this is represented by -4 feet.
So, the total number of feet dug below ground level is thus -3 feet + (-2 feet) + (-4 feet) = -3 feet - 2 feet - 4 feet = -9 feet.
b. Since the sum is -9 feet, the negative implying below ground level. So, we have that the hole is 9 feet below ground level. That is, 9 feet deep.
