The reason it's A is because to make the ratio 1:1 you need to have a whole number you can't have half a pencil or pen, so what you need to do is add 22 and 96 and divide you should get 59, but if you add 23 to 96 and divide you get 59.5 and you can't have half a pencil (you can but that's not what were looking for). So in problems like this add and then divide by 2 and choose whole numbers because you can't have half in ratios cause that won't give the correct answer.

8 0

2 years ago

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H=255-21t-16t^2 PLEASE HELP!!

Colt1911 [192]

Answer:

3.15 seconds is the answer.

Explanation

when the ball touches the ground, h =0

hence,

0=255-21t-16t²

16t²+21t-225=0

here a=16 ,b=21, c= -225

$t= \frac{ - b± \sqrt{ {b }^{2} - 4ac} }{2a} \\ \\ t= \frac{ - 21± \sqrt{ {21}^{2} - 4 \times 16 \times - 225} }{2 \times 16} \\ = \frac{ - 21 ± \sqrt{441 - ( - 14400)} }{32} \\ = \frac{ - 21± \sqrt{14841} }{32} \\ = \frac{ - 21±121.82}{32} \\ \\ t = \frac{ - 21 + 121.82}{32} \: or \: \: t = \frac{ - 21 - 121.82}{32} \\ t = 3.15 \: \: or \: \: t = - 4.46$

time cannot be negative, hence t = -4.46 can be avoided

The ball takes 3.15 seconds to hit the ground.

4 0

2 years ago