5.3 Applied Arithmetic from Supplied Data

5.3 Applied Arithmetic from Supplied Data

Core skill: Turn numbers and rules given in a question into a calculation. The CBSA says prior agency knowledge is unnecessary, so these exercises use fictional rates and thresholds stated in full; they are not lessons in actual customs tariffs or personal exemptions.

Translate the question before calculating

Many analytical items look harder because they wrap a short calculation in a long narrative. Write down the unit, the base and the requested output. A percentage applies to the stated base; a threshold comparison requires subtracting the threshold only if the hypothetical rule says to do so. Distinguish “percentage of total” from “percentage increase,” and track whether a quantity is a count, a rate per hour, or an amount of money.

Worked calculation: a fictional threshold

For this exercise only, a warehouse policy states that the first 800 units of value are exempt and any excess is assessed at 8%. A shipment has a stated value of 1,100 units. The excess is 1,100 − 800 = 300. The assessment is 300 × 0.08 = 24 units. The threshold, rate and applicability were all supplied by the question. If the stem had instead said the rate applied to the entire 1,100 units, the result would be 88 units. Reading the base matters more than memorizing any real-world border figure.

Worked calculation: two units and a time rate

A report gives a scanner rate of 14 parcels per minute and a running time of 2 hours 25 minutes. Convert time first: 2 × 60 + 25 = 145 minutes. Then 145 × 14 = 2,030 parcels. If the scanner paused for 15 minutes, subtract that interval before multiplication: 130 × 14 = 1,820. A frequent error is multiplying 14 by 2.25 as if 25 minutes were one quarter of an hour; they are not. Another is ignoring an explicit pause.

For currency conversion practice, the question must give the exchange rate and direction. At a hypothetical rate of 1 foreign unit = 1.30 Canadian units, 850 foreign units are 850 × 1.30 = 1,105 Canadian units. If the rate were expressed in the reverse direction, division rather than multiplication could be required. Write the units beside each factor to see which cancel.

Sanity checks

• Convert 8% to 0.08, not 0.8.
• A 20% rise followed by a 20% fall does not return to the starting value: 100 becomes 120, then 96.
• Check whether the denominator for a rate comparison is workers, hours, lanes, or cases.
• Compare the selected option with a quick estimate to catch a misplaced decimal.

These methods transfer to tables, reports and everyday data. No real customs duty rule is assumed.