Mathematics, 18.09.2019 06:30 hernandez48tur

Is y=7.5x a proportional relationship and why

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Direct Proportion functions look like this:

y=kx

'k' is the constant of proportionality and in this case its 7.5 or 15/2.

When x=1, y=7.5
When x=2, y=15
When x=3, y=22.5

Therefore y is directly proportional to x.

DIRECT PROPORTION EXPLAINED:

Say a football costs £7.50. If you buy one football you'll have to pay out £7.50, but if you you buy two footballs you'll have to pay out £15.00. Therefore the cost of the football(s) is directly proportional to the amount of footballs you buy. C=cost, f=football(s) and C∝f, therefore C=kf, but as k=7.5, C=7.5f.

INVERSE PROPORTION EXPLAINED:

If it were to take 8 hours for one bricklayer to set up a wall, how long would it take for two bricklayers to set up a wall? The answer in this case would be 4 hours.

T=time to set up a wall
b=bricklayer(s)

Therefore T∝1/b, and T=k/b. In this case k=8 so T=8/b.

When b=1, T=8.
When b=2, T=4.

We'd say that the time it would take for bricklayers to set up a wall would be inversely proportional to the amount of bricklayers available.

Answer from: Quest

Answer: choice c and choice d

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explanation

the graph has a slope of 1/3 because each time you move up 1, you go to the right 3. so, slope = rise/run = 1/3. we can cross choice a off the list since we want a slope of 3, rather than 1/3.

the first table shown has a slope of -3. this is because the rise is -6 and the run is 2, so slope = rise/run = -6/2 = -3. note how x increases by 2 each time (run) and y drops by 6 each time (rise). choice b can be eliminated.

the second table has a slope of 3. each time x goes up by 1, the y values increase by 3. slope = rise/run = 3/1 = 3. alternatively you can use the slope formula to prove that the slope is 3 here. use any two rows of values to generate the two points. choice c is one of the answers

the third table also has a slope of 3. let's use the slope formula to prove as such. i'm going to use the first two rows of the table. so i'll use the two points (2,1) and (5,10)

m = slope

m = (y2-y1)/(x2-x1)

m = (10-1)/(5-2)

m = 9/3

m = 3 so we get a slope of 3

choice d is the other answer

Which functions have an additive rate of change of 3? check all that apply

Answer from: Quest

the highest percentage for deaths in construction from highest to lowest is as follows: falls, struck by objects, electrocution, and caught-in/between. these four are collectively known as fatal four.

in the case of falls, the type that is responsible for the overall highest death in the category is falls from roofs.

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