Med math · 5 free problems
Weight-based problems have two traps: forgetting to convert pounds, and confusing a per-dose rate with a per-day total. Read for the words per dose and per day before you calculate.
Fictional labels. Round as each question says. How to round
Question 1 of 5
A practice problem gives a weight of 143 lb. Convert it to kg using the exercise's approximation of 1 kg = 2.2 lb. Give the exact result using that supplied factor; no rounding is needed.
Answer: 65 kg.
143 lb × (1 kg / 2.2 lb) = 65 kg.
Check: 65 kg × 2.2 lb/kg = 143 lb.
If you got 314.6 kg: You multiplied by 2.2. To cancel lb and leave kg, place lb in the denominator of the conversion factor.
Question 2 of 5
A fictional weight-based exercise specifies 12 mg/kg per dose and a weight of 22.5 kg. How many mg does the exercise specify for one dose? Give the exact answer in mg per dose; no rounding is needed. Use only the stated exercise values; this is not a recommended medication regimen.
Answer: 270 mg per dose.
22.5 kg × (12 mg / kg / dose) = 270 mg/dose. The kg units cancel. The question already states an amount per dose.
Check: 270 mg/dose ÷ 22.5 kg = 12 mg/kg/dose.
If you divided by a number of daily doses: No daily total is given here. “Per dose” already describes each dose.
Question 3 of 5
A fictional weight-based exercise specifies a total of 18 mg/kg per day, divided into three equal doses per day. The given weight is 31.5 kg. How many mg are in each dose? Give the exact answer in mg per dose; no rounding is needed. This is an arithmetic exercise using a supplied regimen.
Answer: 189 mg per dose.
First find the daily total: 31.5 kg × 18 mg/kg/day = 567 mg/day. Then divide: (567 mg/day) ÷ (3 doses/day) = 189 mg/dose.
Check: 189 mg/dose × 3 doses/day = 567 mg/day; 567 mg/day ÷ 31.5 kg = 18 mg/kg/day.
If you got 567 mg per dose: That is the daily total. The question asks for one of three equal doses.
Question 4 of 5
A fictional weight-based exercise specifies 5 mg/kg per dose for a weight of 66 lb. Convert the weight using the exercise's approximation of 1 kg = 2.2 lb, then find the mg per dose. Give the exact answer in mg per dose; no rounding is needed. Use only the stated exercise values; this is not a recommended medication regimen.
Answer: 150 mg per dose.
First 66 lb × (1 kg / 2.2 lb) = 30 kg. Then 30 kg × (5 mg / kg / dose) = 150 mg/dose.
Check: 150 mg/dose ÷ 5 mg/kg/dose = 30 kg; 30 kg × 2.2 lb/kg = 66 lb.
If you got 330: You multiplied 66 by 5 without converting pounds to kilograms. The rate is per kilogram.
Question 5 of 5
A fictional weight-based exercise specifies a total of 24 mg/kg per day, divided into four equal doses per day. The given weight is 45 kg. How many mg are in each dose? Give the exact answer in mg per dose; no rounding is needed. This is an arithmetic exercise using a supplied regimen.
Answer: 270 mg per dose.
Daily total: 45 kg × 24 mg/kg/day = 1,080 mg/day. Per dose: (1,080 mg/day) ÷ (4 doses/day) = 270 mg/dose.
Check: 270 mg/dose × 4 doses/day = 1,080 mg/day; 1,080 mg/day ÷ 45 kg = 24 mg/kg/day.
If you got 1,080 mg per dose: That is the daily total. Divide it by the number of doses in the day.
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