Estimate: 29.5% of 1800 is what number?

Re: Estimate

"Of" means "times". Depending on how close you want your approximation to be you might approximate 29.5% to be 30% or 25%. Of course 25% is 1/4.
 
Round to the nearest whole number, in this case 30%. Convert the percentage to a decimal and multiply

.30 * 1800 will be your estimate.

You can do some simple mental math to get this answer (the whole idea of estimating)

Ignore the zeros and decimal for now, and add them on at the end.

3*18

Break up the 18 into 10 and 8.
3 * 10 = 30;
3 * 8 = 24.
30 + 24 = 54

add the zeros back on: 5400. Remember that you were really multiplying by .3 (not 3), so move the decimal one to the left to account for this.

Your final estimate is 540.
 
easier to do is cross multiplying.

29.5%/100% = x/1800, cross multiply and solve for x
 
jjm5119 said:
easier to do is cross multiplying.
Click to expand...
But in pre-algebra, we cannot make the assumption that the student has encountered variables yet, or knows how to solve equations. :oops:

Eliz.
 
...and it is hoped the beginning student never again hears the words "cross-multiply". Now I have to go wash my keyboard.
 
It's confusing and leads to far more errors than it's worth. Just learn to solve equations by multiplication. Why invent a new rule? I never liked the "special" solution for proportions, either, you know it, "product of the means and the extremes"? Just learn to multiply. It is quite sufficient.

My views. I welcome others'.

My estimate:

1800

10% of that is 180

3*180 is 540

So, 520.

Let's see 0.295*1800 = 531

There are many ways to do many things.
 
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