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3 years ago

Dave is three times as old as his sister. In seven years the sum of their ages will be 38. How old are they now?

Mathematics

1 answer:

bija089 [108]3 years ago

7 0

Answer:

Dave is 18 and his sister is 6.

Step-by-step explanation:

If you do 38 -7x2 you can work out the combined ages of them now which is 24 (you have to do 7x2 because there are two of them and its seven years in the future). Then you can work out their ages using a ratio. Dave’s age : his sister’s age is 3:1 so if you divide 24 by 4 (3+1 = 4 so your can work out one portion of their age) you can find out how old the sister is which is 6. Times that by 3 to get Dave’s age which is 18. A formula for this (where x is his sisters age) would be 3x=38-7x2 which cancels down to 6.

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vampirchik [111]

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Step-by-step explanation:

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OlgaM077 [116]

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2 years ago

Y=x-5; domain = {4,6,8}

Lostsunrise [7]

Answer:

Range = {-1, 1, 3}

Step-by-step explanation:

<u><em>The question asks for the range.</em></u>

The function given is

$y=x-5$

The domain is the set of 3 numbers:

Domain = {4,6,8}

We need to find the range.

First, the range is the set of all y-values for which the function is defined.

When we will be given the domain with a set of numbers, the range would be the numbers that we get when we evaluate the the function at those numbers.

So, we evaluate the function (y-values) at x = 4,6, and 8.

At x = 4:

$y=x-5\\y=4-5\\y=-1$