Andros has an oil fired heating system. In 30 days period he used a full tank of oil at a constant rate per day . At a different time of the year the amount of oil andros uses per day is 1/3 of the rate used in 30 days period . How many days should a full tank of oil last at this new rate

90 days

Step-by-step explanation:

Let the rate per day for the 30 days period be x

Given that the rate drops to 1/3 of the rate used in 30 days period, it means that the new rate

= 1/3 x

If at a rate of x, the full tank runs for 30 days

at a rate of 1/3 x, the full tank would run for

= x/ (1/3 x) * 30 days

= 3 * 30 days

= 90 days

At the new rate, the full tank of oil will last for 90 days

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this