Answer:
The piano was in the air for 18.34 seconds.
Step-by-step explanation:
The height of the piano after t seconds is given by the following equation:
Initially, the piano is below the ground level. At the first root of the equation, it will go into the air, and then some time after that it will fall down again, which is at the second root of the equation.
Roots of a quadratic equation:
Given a second order polynomial expressed by the following equation:
.
This polynomial has roots 
such that 
, given by the following formulas:
In this question:
So
Subtracting:
19.17 - 0.8348 = 18.34
The piano was in the air for 18.34 seconds.
Answer and explanation:
Since a quarter(1/4) of paint covers 80 square feet, a whole paint would cover 80×4= 320 square feet of the wall
Remaining part of the wall left unpainted after using one whole paint
480-320= 160 square feet
Therefore paint required for remaining unpainted part
= 160/80= 2 quarters of paint(1/4+1/4)= 1/2 paint
Total paint required for the wall = one whole paint + half paint = 1+1/2= 1 1/2
Total paint required is one and half
Or
We divide area of wall by area of wall covered by each quarter
480/80=6 quarters of paint
6 quarters of paint = 1/4+1/4+1/4+1/4+1/4+1/4
We still get same answer
= 1 1/2
