Toolbox Math – Basic Math for Trades

1. A construction site requires 485 bricks for a retaining wall. If the bricks are delivered in pallets of 60, how many full pallets must be ordered to ensure there are enough bricks?

a. 8
b. 8.08
c. 9
d. 7

2. An electrician installs 14 outlets on the first floor, 19 on the second floor, and 12 in the basement. If each outlet takes 15 minutes to install, how many minutes total will the installation take?
a. 45 minutes
b. 600 minutes
c. 675 minutes
d. 725 minutes

3. Evaluate the following expression using the order of operations: $12 + (8 X 5) – 10 \ 2
a. 47
b. 95
c. 20
d. 55

4. A carpenter needs to cut a board to 15 3/8 inches. The board is currently 18 1/2 inches long. How much needs to be cut off?

a. 3 1/8 inches
b. 3 1/4 inches
c. 2 7/8 inches
d. 3 1/2 inches

5. Convert 0.625 into a fraction in its simplest form.
a. 3/5
b. 5/8
c. 2/3
d. 6/10

6. A concrete mix requires a ratio of 1 part cement to 3 parts sand. If you have 40 kg of sand, how much cement do you need (rounded to the nearest whole number)?

a. 10 kg
b. 12 kg
c. 13 kg
d. 15 kg

7. A contractor estimates a job will cost $4,500. If he adds a 15% contingency fee for unexpected costs, what is the new total estimate?
a. $5,000
b. $4,675
c. $5,175
d. $6,750

8. How many inches are in 6 feet 4 inches?
a. 72 inches
b. 76 inches
c. 64 inches
d. 78 inches

9. Calculate the area of a rectangular workshop floor that measures 12 feet by 15 feet.

a. 54 sq ft
b. 160 sq ft
c. 180 sq ft
d. 27 sq ft

1. C 9
Step 1: Divide total bricks needed by bricks per pallet:  $485 \60 = 8.0833
Step 2: You cannot order 0.08 of a pallet. You must round up to the next whole number to ensure you have enough.
Step 3: Round 8.08 up to 9.

2. C 675 minutes
Step 1: Calculate total outlets: $14 + 19 + 12 = 45 outlets.
Step 2: Multiply total outlets by time per outlet:  45 X 15 mins/outlet.
Step 3: 45 X 15 = 675.

3. A 47
Step 1 (Parentheses): Solve 8 X 5 = 40. The equation is now $12 + 40 – 10 \ 2.
Step 2 (Division): Solve $10 / 2 = 5. The equation is now  $12 + 40 – 5.
Step 3 (Add/Subtract left to right): 12 + 40 = 52.
Step 4: 52 – 5 = 47.

4. A 3 1/8
Step 1: Set up the subtraction: 18 1/2 – 15 3/8}.
Step 2: Find a common denominator for the fractions. The common denominator for 2 and 8 is 8.
Step 3: Convert 1/2 to eighths: (1 X 4)/ (2 X 4} = 4/8.
Step 4: Now subtract: 18 4/8 – 15 3/8}.
Step 5: Subtract whole numbers (18 – 15 = 3) then fractions (4/8 – 3/8 = 1/8. Result: 3 1/8.

5. B 5/8
Step 1: Write the decimal as a fraction over 1000 (since there are 3 decimal places): 625/1000.
Step 2: Simplify by dividing top and bottom by 25:  25/40.
Step 3: Simplify again by dividing by 5: 5/8.

6. C 13 kg
Step 1: The ratio is 1 (Cement) : 3 (Sand).
Step 2: Set up the proportion: 1/3 = X (Cement)/40 (Sand).
Step 3: Cross multiply: 3x = 40.
Step 4: Solve for x: 40 / 3 = 13.33.
Step 5: Round to nearest whole number: 13 kg.

7. C $5,175
Step 1: Convert percentage to decimal: 15% = 0.15.
Step 2: Calculate the contingency amount:  $4,500 X 0.15 = 675.
Step 3: Add to the original cost: 4,500 + 675 = 5,175.

8. B 76 inches
Step 1: Know the conversion: 1 foot = 12 inches.
Step 2: Convert feet to inches: 6 feet X 12 = 72 inches.
Step 3: Add the extra inches: $72 + 4 = 76 \text{ inches}$.

9. C 180 sq ft
Step 1: Formula for Area of a rectangle = Length times Width.
Step 2: 12 X 15.
Step 3: 12 times 10 = 120; 12 times 5 = 60; 120 + 60 = 180. Result: 180 sq ft.