A projectile is thrown upward so that its distance above the ground after t seconds is h = -16t^2 + 672t. After how many seconds does it reach its maximum height?

$4

step-by-step explanation:

$30×5=$150

$150 minus $130=$20

$20÷5=$4.

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probably the last option

step-by-step explanation:

the 8 in 8,420 is in the thousands place so it's value is 8 thousand.

the 8 in 6,870 is in the hundreds place so it's value is 8 hundred.

divide 8000 by 800 to find the answer:

8000 / 800 = 10

the 8 in 8,420 is 10 times greater than the 8 in 6,870