To determine how much force Joaquin saves by using a lever with a mechanical advantage of 3, we first need to calculate the force he would need to apply using the lever.
The mechanical advantage (MA) of a lever is defined as the ratio of the output force (the force needed to lift the crate) to the input force (the force exerted by Joaquin):
\[ \text{MA} = \frac{\text{Output Force}}{\text{Input Force}} \]
Given that the mechanical advantage is 3, we can rearrange the formula to find the input force (the force Joaquin needs to exert):
\[ \text{Input Force} = \frac{\text{Output Force}}{\text{MA}} = \frac{312 \text{ N}}{3} = 104 \text{ N} \]
Now, to find out how much force he saves, we subtract the input force from the output force:
\[ \text{Force Saved} = \text{Output Force} - \text{Input Force} = 312 \text{ N} - 104 \text{ N} = 208 \text{ N} \]
Therefore, the amount of force Joaquin saves by using the lever is 208 N.