A labor and delivery nurse weighs a newborn baby at 3.5 kilograms. How much does the baby weigh in ounces?

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You likely have not memorized how many kilograms are in an ounce, but we do know that 1 kilogram = 2.2 pounds and 1 pound = 16 ounces. This also means that we know the conversion factors to convert between the two systems and units. The conversion factor for switching between kilograms and ounces is ^{2.2 lb} / _{1 kg} (which shows that for every 1 kilogram, we have 2.2 pounds). Similarly, the conversion factor for switching between ounces and pounds is ^{16 oz} / _{1 lb.} First, we need to convert the kilograms to pounds, which we do by multiplying the number of kilograms by the conversion factor: 3.5 kg • ^{2.2 lb}/_{1 kg} → Remember that all whole numbers can be written as a fraction with "1" as the denominator. When multiplying a whole number by a fraction (especially in unit conversion problems), you can rewrite the whole number as a fraction in this way in order to make simplification easier. = ^{3.5 kg}/₁• ^{2.2 lb}/_{1 kg} → Next, multiply the two fractions by multiplying the two numerators, then the two denominators. =^{3.5 kg • 2.2 lb}/_{1 • 1 kg} → At this stage, you can also cancel out any units that are present in both the numerator and the denominator (basically, you're dividing a unit by itself, so they cancel out). =^{3.5 kg • 2.2 lb}/_{1 • 1 kg} = ^{3.5 • 2.2 lb}/₁ = ^{7.7 lb}/₁ = 7.7 lb → Now, we need to convert the pounds to ounces, using the same method. 7.7 lb • ^{16 oz}/_{1 lb} → Remember that all whole numbers can be written as a fraction with "1" as the denominator. When multiplying a whole number by a fraction (especially in unit conversion problems), you can rewrite the whole number as a fraction in this way in order to make simplification easier. = ^{7.7 lb}/₁• ^{16 oz}/_{1 lb} → Next, multiply the two fractions by multiplying the two numerators, then the two denominators. =^{7.7 lb • 16 oz}/_{1 • 1 lb} → At this stage, you can also cancel out any units that are present in both the numerator and the denominator (basically, you're dividing a unit by itself, so they cancel out). =^{7.7 lb • 16 oz}/_{1 • 1 lb} = ^{7.7 • 16 oz}/₁ = ^{123.2 oz}/₁ = 123.2 oz The weight of the baby in ounces is 123.2 oz.

A Labor and Delivery Nurse Weighs a Newborn Baby at 3.5