Energy - 7th grade (12y) - examples

  1. Excavation
    vykop_ryha 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
    tanks 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
    gas_meter 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
    gas_car 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_motor Car traveling at 130 km/h on the highway. Pulling power of the motor is 8 kN. Determine engine power in kW.
  6. Cows
    kravy0 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
    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
    fuel2 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
    rychlovarna-kanvica What is the power output of kettle 2 kW with efficiency 90%?
  10. Ounce
    energy_1 749 calories in a 7 - ounce serving . What is the unit rate?
  11. Electric energy
    bulb _3 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
    fries 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
    plynomer Gas consumption for 2017 was 11,301 kWh I paid 532 € How much 1 m3?
  14. Gasoline price
    fuel_pump2_1 At 34.4 cents per liter, how much will 42 liters of gasoline cost?
  15. Calories 2
    energy_2 Ben eats approximately 2400 calories per day. His wife Sarah eats 5/8 as much. How many calories does Sarah eat per day?

Do you have an interesting mathematical example that you can't solve it? Enter it, and we can try to solve it.

To this e-mail address, we will reply solution; solved examples are also published here. Please enter e-mail correctly and check whether you don't have a full mailbox.