Annn G.
asked • 07/08/20Please I need an answered quickly
James L. answered • 07/11/20
Tutoring for AP and IB Physics and SAT Math
Basic formula is D = rt, where D = distance, r = rate and t = time. We want t, so we divide both sides by r to get t = D / r.. So plugging in 45 we get t = D / 45
So, as example if we put D = 45, we get t = 45 / 45 = 1 hour.
If we put D = 90, we get t = 90 / 45 = 2 hours. And so on.
Michael S. answered • 07/08/20
Engineering, Education Student, Statics, Calculus, Materials, Thermo.
If we look at the units we have mi/h ; mi ; and we want to get to h
The only way to get to remove miles from the mi/h and mi is to divide one by the other.
Because we want hours to be in the numerator we should divide by mi/h.
d (mi) / 45 (mi/h) = d/45 (mi * h / mi) = d/45 hours
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David M.
Great. I love using unit manipulation for understanding and as an aid to knowing that you got it right. Another way look at the unit manipulation is that you ultimately want hours, h, so we need h in the numerator; but we are given 45mi/h, with h in the denominator. So instead of 45mi/h, we work with it's reciprocal (1h/45mi). Since, to get h by itself, we now need to get rid of the mi unit in the denominator that is dividing the h in the numerator. To do this, we know that we have to do the reverse operation from division by mi, which is multiplication by d*mi, where d is the variable for distance, mi is the unit for miles, and * is multiplication. (1h/45mi)*(d*mi)= (d/45)*(mi/mi)*h= (d/45)(1)h= (d/45)h or d/45 hours.07/12/20