# Energy - 7th grade (12y) - examples

1. Excavation
Mr. Billy calculated that excavation for a water connection dig for 12 days. His friend would take 10 days. Billy worked 3 days alone. Then his friend came to help and started on the other end. On what day since the beginning of excavation they met?
2. Water
Mix 68 l of water with temperature of 87 °C, 17 l warm of 42 °C and 55 l water of 50 °C. What is the temperature of the mixed water immediately after mixing?
3. Rates
When gas consumption, the consumer may choose one of two rates: rate A - which pays 0.4 € per 1 m3 of gas a flat monthly fee of 3.9 € (regardless of consumption) rate B - which pays 0.359 € per 1 m3 of gas a flat monthly fee of 12.5 € From what monthl
4. Three drivers
Three driversdriving the same direction found that they have same amounth of gasoline. The first is enough to go 6 km, 4 km second and third 3km. Gasoline they divided so all three just drove to the nearest petrol station. How many km away was a petrol sta
5. Motor physics
Car traveling at 130 km/h on the highway. Pulling power of the motor is 8 kN. Determine engine power in kW.
6. Cows
20 cows has food for 60 days. We reduce the dose to two-thirds for 18 cows. How many days will be fed?
7. MPG
252 miles a week fills up twice a week. Each fill is 38 gallons. What is gas mileage of the car?
8. Fuel mileage
You have 3/8 tank of fuel. Estimate fuel consumption @ 6mpg. Estimate speed @ 50mph. Your fuel tank holds 200 gals. Figure out fuel mileage.
9. Efficiency
What is the power output of kettle 2 kW with efficiency 90%?
10. Ounce
749 calories in a 7 - ounce serving . What is the unit rate?
11. Electric energy
There are 875 identical light bulbs in the sports hall lighting for 2 hours. How long does the same amount of electricity consume 100 such bulbs?
12. Calories
A large order of McDonald’s french fries has 500 calories. Of this total, 220 calories are from fat. Find the ratio of the calories from fat to total calories in a large order of McDonald’s french fries.
13. Natural gas in kWh
Gas consumption for 2017 was 11,301 kWh I paid 532 € How much 1 m3?
14. Gasoline price
At 34.4 cents per liter, how much will 42 liters of gasoline cost?
15. Calories 2
Ben eats approximately 2400 calories per day. His wife Sarah eats 5/8 as much. How many calories does Sarah eat per day?

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