Algebraic Expressions Part 3

[mathdad]

1. Translate "nine less than the total of a number and forty" into an algebraic expression, and simplify.

2. The length of a football field is 30 yards more than its width. Express the length of the field in terms of its width w.

3. One hundred gallons of crude oil were poured into two containers of different size. Express the amount of crude oil poured into the smaller container in terms of the amount g poured into the larger container.

My answers given below.

1. Let n = a number

(n + 40) - 9

2. w + 30 or 30 + w

3. I am not too sure about the wording here.

 

[Deleted member 4993]

1. Translate "nine less than the total of a number and forty" into an algebraic expression, and simplify.

2. The length of a football field is 30 yards more than its width. Express the length of the field in terms of its width w.

3. One hundred gallons of crude oil were poured into two containers of different size. Express the amount of crude oil poured into the smaller container in terms of the amount g poured into the larger container.

My answers given below.

1. Let n = a number

(n + 40) - 9

2. w + 30 or 30 + w

3. I am not too sure about the wording here.

3. One hundred gallons of crude oil were poured into two containers of different size. Express the amount of crude oil poured into the smaller container in terms of the amount g poured into the larger container.

Let us define

The amount poured in the smaller (petit) container = p

then we know:

g + p = 100

Hence:

p = 100 - g

 

[mathdad]

3. One hundred gallons of crude oil were poured into two containers of different size. Express the amount of crude oil poured into the smaller container in terms of the amount g poured into the larger container.

Let us define

The amount poured in the smaller (petit) container = p

then we know:

g + p = 100

Hence:

p = 100 - g

Nicely done. More math later....

 

[Otis]

1. Translate "nine less than the total of a number and forty" into an algebraic expression, and simplify.

... Let n = a number

(n + 40) - 9 ...

That's a good start. Now finish it.

?

 

[mathdad]

That's a good start. Now finish it.

?

(n + 40) - 9

n + 40 - 9

n + 31

 

[Steven G]

1. Translate "nine less than the total of a number and forty" into an algebraic expression, and simplify.

2. The length of a football field is 30 yards more than its width. Express the length of the field in terms of its width w.

3. One hundred gallons of crude oil were poured into two containers of different size. Express the amount of crude oil poured into the smaller container in terms of the amount g poured into the larger container.

My answers given below.

1. Let n = a number

(n + 40) - 9

2. w + 30 or 30 + w

3. I am not too sure about the wording here.

Although both answers for (2) are correct (except you did not write l=)I think that it is better to say l= w+30. The reason is that subtraction does not commute like addition.

 

[Otis]

... I think that it is better to say l= w+30. The reason is that subtraction does not commute like addition.

I need help understanding the reason.

?

 

[Steven G]

I need help understanding the reason.

?

If a students thinks that a more than b is a + b, then they have every right to think that a less than b is a - b, which of course is wrong. Besides when we get right down to it, a more than b is b+a and not a+b
If you asked a student (one who is learning how to translate) how to write 4 more than the sum of a number and 8 you do not want them to write n+12.