Solution
To solve division problems you can make equal groups
Example

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Answer:
At 65 mph, keeping one second of following distance means the vehicle is traveling 100 feet behind the vehicle in front. It takes an automobile a minimum of 150 feet to stop. With a 100 foot gap plus the auto's stopping distance of 150 feet, an impact would occur within 250 feet.
Blue triangle: perimeter is 4x+2+7x+7+5x-4, or, after simplification,
16x + 5
Red triangle: perim. is 2x-5+x+7+x+3 (and so on).
Start with 180.
<span>Is 180 divisible by 2? Yes, so write "2" as one of the prime factors, and then work with the quotient, 90. </span>
<span>Is 90 divisible by 2? Yes, so write "2" (again) as another prime factor, then work with the quotient, 45. </span>
<span>Is 45 divisible by 2? No, so try a bigger divisor. </span>
<span>Is 45 divisible by 3? Yes, so write "3" as a prime factor, then work with the quotient, 15 </span>
<span>Is 15 divisible by 3? [Note: no need to revert to "2", because we've already divided out all the 2's] Yes, so write "3" (again) as a prime factor, then work with the quotient, 5. </span>
<span>Is 5 divisible by 3? No, so try a bigger divisor. </span>
Is 5 divisible by 4? No, so try a bigger divisor (actually, we know it can't be divisible by 4 becase it's not divisible by 2)
<span>Is 5 divisible by 5? Yes, so write "5" as a prime factor, then work with the quotient, 1 </span>
<span>Once you end up with a quotient of "1" you're done. </span>
<span>In this case, you should have written down, "2 * 2 * 3 * 3 * 5"</span>