Answer:
The minimum average speed needed in the second half is 270 km/hr
Step-by-step explanation
We can divide the track in two parts. For the first half of the track the average speed the car achieved was 230 km/hr and we need to make sure that the average speed of the full track is 250 km/hr. Then, we can calculate the average speed of the two parts of the track and force this to be equal to 250 km/hr. In equation, defining 
as the average speed of the second half:
Solving for 
Therefore, achieving a speed of 270 km/hr in the second half would be enough to achieve an average speed of 250 on the track.
Answer: a = 162
Step-by-step explanation:
The percentage of students who spend less than 4 hours a week on screens which reported a grade average below 80 is 50%
Given, we have the report representing children spending time online, on social media or watching T.V, which has there effect on there grades as above or below 80.
By the question we know that the number of students who spends less than 4 hours a week on screen is:
9 + 9
= 18
And among the 18 students there are 9 students whose grade average is below 80.
So the percentage of the students who spends 4 hours a week on screen is:
= 9 ÷ 18 × 100%
= 100/2
= 50%
hence 50% students spend less than 4 hours a week on screens.
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You take the first number 261 then take the second number 76 times them together and you will get 19,836
Given that,
Total number of snails shells and shark teeth = 60
The ratio of snail shells to shark teeth is 5:1
To find,
Total no of snail shells used by the Jeweler.
Solution,
Let there are 5x snail shells and x shark shells.
According to question,
5x+x = 60
6x = 60
x = 10
Snail shell = 5x
= 5(10)
= 50
Hence, he uses 50 snail shells.
