Answer:
50X ≤ 400
50X ÷ 50 ≤ 400 ÷ 50 (to get X, divide both sides by 50)
X ≤ 8
∴ The wheelbarrow can carry at most 8 (eight) 50-pound bags of concrete.
Explanation:
If we represent the unknown number of concrete bags as X, then we can rephrase the question as:
How many 50 pounds of X (concrete bags) can almost or completely fill my 400 pounds wheelbarrow? This is exactly the meaning of the inequality:
50X ≤ 400
Where the ≤ is the same as saying almost or completely, and X is the number of concrete bags we would like to find that can 'almost or completely' fill our 400 pounds wheelbarrow.
You can verify this by pretending to put a single 50-pound bag of concrete into your 400 pounds wheelbarrow one at a time.
After the first 50-pound bag of concrete, your wheelbarrow will only have space for 350 pounds more.
If you add another 50-pound bag, this time your wheelbarrow will only have 300 pounds of space left.
Adding another 50-pound bag, your wheelbarrow is left with only 250 pounds of space.
You should continue to do this until you have zero or no space left in the wheelbarrow, and then count the number of 50-pound concrete bags you were able to fit into your wheelbarrow.
In the end, you'll have moved 8 bags of 50-pound concrete. You can verify by multiplying 50 by 8 which will give 400.
As an exercise, try doing this with a 40-pound and 30-pound of concrete bags and let me know what you find.