Question

A 750 Watt hairdryer is used for 15 minutes. Calculate the Kwhr used. Calculate the cost to use 15 min. every day for 1 year @ 8 cents/Kwhr

Answer 1

Part (a):
We know that:
1 kw = 1000 watt ..........> Therefore, to convert watt into kw, we will divide by 1000
1 hour = 60 min ..........> Therefore, to convert mins into hours, we will divide by 60
Based on the above, the conversion results for the two units together would be as follows:
1 watt minute is equivalent to 0.000017 kilowatt hours
Now, for the given , we will simply use cross multiplication to do the conversion as follows:
1 watt minute..............> 0.000017 kilowatt hours
750*15 ................> ??
750*15 watt min = 0.19125 kilowatt hour

Part (b):
From part a, we have that the consumption is 0.19125 kilowatt hour per day. Assuming that the year is 365 days, we would have:
yearly consumption = 0.19125 * 365 = 69.80625 kilowatt hour
The cost is 8 cents/kilowatt hour
Therefore:
yearly cost = 69.80625 * 8 = 558.45 cents

Hope this helps :)

Answer 2

Answer:

1) 0.1875 kWhr

2) $5.475

Explanation:

1) To convert 750 Watt to kWhr, firts we convert watt to kilowatt

750 W in kW = $\frac{750}{1000} = 0.75$kW

To calculate the amount of power used in kWhr, we multiply the power rating (0.75 kW) by the number of time spent in hours (15 mins).

To convert 15 mins to hour,

15 mins in hr = $\frac{15}{60} = 0.25$hr

The kWhr used = 0.75 x 0.25 = 0.1875 kWhr

2) If used 15 mins everyday for a year, first we calculate the total amount of power used for 365 days

Daily usage at 15 mins = 0.1875 kWhr

Yearly usage = 0.1875 x 365 = 68.4375 kWhr

Cost of usage for a year at 8 cents per kWhr is;

68.4375 x 8 = 547.5 cents

Cost of usage = $5.475 per year