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A calorie is a unit of energy. In sustenance, calories allude to the energy individuals get from the food and drink they polish off, and the energy they use in active work. Calories are recorded in the nourishing data on all food bundling. Many health improvement plans are based on lessening the admission of calories.

Given,

time for swimming is $2.5hr$and time for walking is $8hr$

calories burned while swimming = $340kcal$

calories burned while walking = $160kcal$

role="math" localid="1652019330115" $\text{Total}\text{kcalexpended}=\text{Energy spent due to swimming}+\text{Energy spent due to walking}$

$=2.5\mathrm{h}×340+8.0\mathrm{h}×160=2130kcal$

Loss of $1lb$took $3500kcal$

total energy is $2130kcal$

total weight lost,

$\frac{2130}{3500}=0.608lb$

$160kcal$burned while walking for $1hr$

Total calories to be burned = $3500kcal$

The time taken to burn them,

$\frac{3500}{160}=22h$

Given,

calories required to burn$1lb=3500kcal$

calories burned per hour while swimming =$340kcal$

Time taken for Charles to lose $1lb$while swimming =

$\frac{3500}{340}=10.3\mathrm{hr}$