Answer:
86%
Step-by-step explanation:
Let g represent the mean mark for the 10 girls in the class. Then the mean mark for the class was ...
10g +20(62%) = 30(70%)
g = 3(.7) -2(.62) . . . . . . . . . divide by 10 and subtract 2(.62)
g = .86 = 86%
The mean mark for girls was 86%.
_____
You can do this in your head if you consider it in terms of deviations from the mean. The second equation above can be rewritten and factored as ...
g = 70% +2(70% -62%)
That is, because there are 2 boys for every girl, the girl's score is above the mean by an amount that is 2 times the amount that the boy's score is below the mean. The boys' score is below by 8%, so the girls' score is above by 16%, so is 86%.
Answer:
2x+3
Step-by-step explanation:
-2x2 - 7x - 6
--------------------
-x-2
-2x2 - 7x - 6 = -1 • (2x2 + 7x + 6)
-x - 2 = -1 • (x + 2)
2x2 + 7x + 6
x • (2x+3) and (x+2) • (2x+3)
answer- 2x+3
Answer:
Step-by-step explanation:
Product of of 3 and b is 3b
At least means greater than or equal too.
Answer:
1920
Step-by-step explanation:
Each time you multiply by to 6 times. 30 does not count as a year.
