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A red kite is 100 feet off the ground and is rising 8 feet per second. a blue kite is 180 feet off the ground and is rising 5 feet per second. how long will it take for the red kite to be higher than the blue kite

Respuesta :

from the information given you can form two linear equations. 
Red kite: Y = 8x + 100 
Blue Kite: Y = 5x + 180 

you are looking for where these two lines intersect on a graph. 

Each equation gives you a value of y so you can take one and put it in the place of the other 

Ex., 8x + 100 = 5x +180 

rearrange this and you get 3x - 80 = 0

then isolate x:
1) 3x = 80 
2) x = 80/3
3) x = 26.7


Now, put your X value into either of the original equations to find Y

Y = 8x + 100
Y = 8(26.7) + 100
Y = 313.6

to check your answer you can do a simple left side right side check 

313.6 = 5(26.7) + 180 

313.6 = 133.5 + 180

313.6 = 313.5 

** this counts as correct, the difference in decimal is due to rounding 

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