Question

Bill's recipe for onion soup calls for $4.0$lb of thinly sliced onions. If an onion has an average mass of $115\mathrm{g}$, how many onions does Bill need? (2.6)

Short answer

Bill needs a total of $16$onions when the average mass of onions is $115g$

Step-by-step solution

Introduction 

The given is the weight required for Bill for his onion soup

The objective is to determine the number of onions purchased by Bill

Step 1

Given,

Onion mass average is $=115\mathrm{g}$

The total amount of onion needed to make onion soup $=4.0\mathrm{lb}$

Conversion factor:-

$1\mathrm{lb}=454\mathrm{gm}$

The total amount of onion needed to make onion soup is,

$4.01\mathrm{b}\times \frac{454\mathrm{gm}}{1\mathrm{lb}}=18614\mathrm{gm}$

Step 2

To make onion soup, you'll need a certain number of onions $=\frac{\text{Total mass of onion required}}{\text{Average mass of onion}}$

$=18614\mathrm{gm}\times \frac{1}{115\mathrm{gm}}$

$=16$ onions (Rounding off two significant figures)