Answer:
T = 960 seconds
Step-by-step explanation:
the equation of the direct proportion is y = k x, where k is the constant of variation, we find it using the initial amount of x and y
∵ T is the time in seconds
∵ m is the mass of water in kg
∵ The time, T it takes a water heater to boil some water is directly
proportional to the mass of the water, m
∴ T = km
∵ When m = 250 kg, T = 600 seconds
→ Substitute them in the equation above to find k
∵ 600 = k(250)
→ Divide both sides by 250 to find k
∴ 2.4 = k
→ Substitute the value of k in the equation above
∴ T = 2.4m ⇒ the equation of the direct proportion
∵ m = 400 kg
→ Substitute it in the equation of variation to find T
∵ T = 2.4(400)
∴ T = 960 seconds
