The best way to multiply complicated problems mentally* is to break them into chunks.
Start with 20 times 8 to get 160, and then 8 times 5 to get 40. Add these together to get 200. 200 times 3 is 600, and 20 times 200 is 4000. Add these together to get your final answer, 4600.
In other words 8 x 20 + 8 x 5 = 200 200 x 3 + 200 x 20 = 4600
*I assumed you meant mentally, because otherwise you'd just multiply longhand, multiplying two of the three numbers and then multiplying their product with the third.
Answer:
1
Step-by-step explanation:
4÷1=4 4×1=4 4+1 = 5 5-1 = 4
Answer:
21 Students
Step-by-step explanation:
140 x .15 = 21
15% of 1560 is 234. 234/0.15=1560 and 1560 x 0.15=234, therefore the answer is 1560.
Answer:
a) 
degrees
b) 
Step-by-step explanation:
An approximate formula for the heat index that is valid for (T ,H) near (90, 40) is:
a) Calculate I at (T ,H) = (95, 50).
degrees
(b) Which partial derivative tells us the increase in I per degree increase in T when (T ,H) = (95, 50)? Calculate this partial derivative.
This is the partial derivative of I in function of T, that is 
. So
