Answer:
77.88 minutes 
Step-by-step explanation:
Given that :
Mean (m) = 70
Standard deviation (s) = 10
For 80% of student to complete the exam. In the given time
Using the formula :
Zscore = (X - mean) / standard deviation
80th percentile = 80/100 = 0.8 has a Zscore = 0.7881
0.7881 = (X - 70) /10
0.7881 * 10 = X - 70
7.881 = X - 70
7.881 + 70 = X
77.881 = X
Hence, 77.88 minutes should be given 
 
        
             
        
        
        
5r=75
r=75/5=15
3f=75
f=75/3
f=25
4d=75
d=75/4
d=18.9
5r+3d+4f+75
        
                    
             
        
        
        
The area is 35. Look at the sketch below for explanation!
 
        
        
        
<span>15 eggs and 16 cups flour </span>
<span>Pumpkin bread (x) : 2 eggs & 3 cups of flour </span>
<span>Coffee cake (y) : 3 eggs & 4 cups of flour </span>
<span>2x + 3y ≤ 15 { number of eggs used} </span>
<span>3x + 4y ≤ 16 { number of cups of flour used } </span>
<span>Objective function </span>
<span>P = 5x + 4y</span>