1 / 3
We will convert 420\,\dfrac{\text{kcal}}{\text{h}}420
h
kcal
420, space, start fraction, k, c, a, l, divided by, h, end fraction to a rate in \dfrac{\text{cal}}{\text{min}}
min
cal
start fraction, c, a, l, divided by, m, i, n, end fraction using the following conversion rates:
There are 60\text{ min}60 min60, space, m, i, n per 1\text{ h}1 h1, space, h.
There are 1000\text{ cal}1000 cal1000, space, c, a, l per 1\text{ kcal}1 kcal1, space, k, c, a, l.
Hint #22 / 3
\begin{aligned} &\phantom{=} \dfrac{420 \text{ kcal}}{1\text{ h}} \cdot\dfrac{1\text{ h}}{60\text{ min}}\cdot\dfrac{1000\text{ cal}}{1\text{ kcal}} \\\\ &=\dfrac{420\cdot 1 \cdot 1000 \cdot \cancel{\text{kcal}}\cdot\cancel{\text{h}} \cdot \text{cal}}{1\cdot 60 \cdot 1\cdot\cancel{\text{h}}\cdot \text{min} \cdot \cancel{\text{kcal}} } \\\\ &=\dfrac{420{,}000}{60}\,\dfrac{\text{cal}}{\text{min}} \\\\ &=7000\,\dfrac{\text{cal}}{\text{min}} \end{aligned}
=
1 h
420 kcal
⋅
60 min
1 h
⋅
1 kcal
1000 cal
=
1⋅60⋅1⋅
h
⋅min⋅
kcal
420⋅1⋅1000⋅
kcal
⋅
h
⋅cal
=
60
420,000
min
cal
=7000
min
cal
Hint #33 / 3
In conclusion, Lúcia is using energy in \dfrac{\text{cal}}{\text{min}}
min
cal
start fraction, c, a, l, divided by, m, i, n, end fraction at a rate of:
7000\,\dfrac{\text{cal}}{\text{min}}7000
min
cal
