The radius of the sphere decreases at the rate of 6 m/ sec
That is, 
Surface Area of the sphere of radius r is given by 
Differentiating with respect to t,


Length and width of rectangle is 15 inches and 6 inches respectively
<h3><u>
Solution:</u></h3>
Given that area of a rectangle is 90 square inch
Ratio of length to the width = 5: 2.
Need to determine length and width of rectangle.
As ratio of length to the width is 5 : 2
Lets assume length of rectangle = 5x inches and width of rectangle = 2x inches.
<em><u>The formula for area of rectangle is given as:</u></em>

Substituting the given value of area of rectangle and assumed value of length and width of rectangle we get:

On solving the above expression for x we get


Hence length and width of rectangle is 15 inches and 6 inches.
The answer is: "2.5 years" .
___________________________________________________
Note: I = P * r * t ; { " Interest = Principal * rate * time "} ;
→ Solve for "t" {"time", in years} ;
Divide each side of the equation by "{P * r}" ;
to isolate "t" on one side of the equation ;
→ I / (P * r) = {P * r * t) / (P * r} ;
to get: " I / (P * r) = t " ;
↔ t = I / (P * r) ;
Given: I = $450 ;
<span>P = $2400 ;
r = 7.5% = 7.5/100 = 0.075 ;
Plug in these values into the formula to solve for the time, "t" :
</span>→ t = I / (P * r ) ;
= $450 / (<span>$2400 * 0.075) ;
= </span>$450 / ($2400 * 0.075) ;
= $450 / $180 ;
= $45 / $18 ;
= ($45 ÷ 9) / ($18 ÷ 9)
= $5 / $2 ;
= 2.5 ;
→ t = 2.5 years.
_______________________________________________________
The answer is: "2.5 years" .
_______________________________________________________
Recall the angle sum identities:


Now,

Divide through numerator and denominator by
to get

Next, we use the fact that
lie in the first quadrant to determine that


So we then have


Finally,
