Answer:
36
Step-by-step explanation:
4 was multiplied 6 times to get 24. Therefore you must multiply 7 by 6 as well.
Mean of a set of numbers is
(sum of the values of the numbers in the set)/(how many numbers in the set)=mean
example
1,2,4
mean is
(1+2+4)/3=7/3
ok
mean of 7 numbers is 21
(7numbers)/7=21
"5 of them are 18,23,21,17"
(mentally do 7-5=2)
2 missing
"one of the remaining is 3/4 of other"
the 2 remaining is x and 3/4x
nmow we have
(18+23+21+17+19+x+3/4x)/7=21
add like terms
(98+1 and 3/4x)/7=21
mulitply everybody by 7
98+7/4x=147
minus 98 both sides
7/4x=49
multiply both sides by 4/7 to clear fraction (7/4 times 4/7=28/28=1, so 1x=x)
1x=196/7
x=28
the other number is 3/4 of this
3/4x=3/4*28=21
the 2 unknowns are 28 arnd 21
Use the quadratic formula -b +/-√(b^2-4(ac)) / 2a
In the given formula a = 7, b = 23 and c = -10
Replace the letters with their values:
-23 +/-√(23^2 -4*(7*-10)) / 2*7
Simplify to get:
x = -23 + √809 / 14 or x = -23 - √809 / 14
Given function:
y=9.5x+62.1
We have to find the number of minutes x, when y=138.1°F
Put value of y in function.
138.1=9.5x+62.1
Subtract 62.1 from both sides.
76=9.5x
Divide both sides by 9.5.
8=x
or
x=8 minutes
Answer: After 8 minutes the temperature of water will be 138.1°
