ANSWER
B. 1.78 x 10⁷ J
EXPLANATION
Given:
• The power of the washer, P₁ = 450 W
,• The power of the dryer, P₂ = 3000 W
,• The time needed to wash one load of clothes, t₁ = 1 hour
,• The time needed to dry those clothes, t₂ = 1.5 hours
Energy is the product of power and time,
[tex]E=P\cdot t[/tex]If the power is given in watts, we have to convert the time to seconds, so that the energy is in Joules. Knowing that 1 hour has 3600 seconds,
[tex]\begin{gathered} t_1=1hour\cdot\frac{3600s}{1hour}=3600s \\ \\ t_2=1.5hour\cdot\frac{3600s}{1hour}=5400s \end{gathered}[/tex]So the energy needed to wash the clothes is,
[tex]E_1=P_1\cdot t_1=450W\cdot3600s=1.62\cdot10^6J[/tex]And the energy needed to dry them,
[tex]E_2=P_2\cdot t_2=3000W\cdot5400s=16.2\cdot10^6J[/tex]So, the total energy needed for the whole cycle is,
[tex]E=E_1+E_2=1.62\cdot10^6J+16.2\cdot10^6J=(1.62+16.2)\cdot10^6J=17.82\cdot10^6J=1.78\cdot10^7J[/tex]Hence, the energy needed to wash the clothes for 1 hour and dry them for 1.5 hours is 1.78 x 10⁷ J.
