Answer:
18
Step-by-step explanation:
A two-digit number (xy) will have the value 10x+y. The sum of its digits is x+y.
You want ...
10x +y = 2(x +y)
1 ≤ x ≤ 9
0 ≤ y ≤ 9
The equation can be simplified to ...
8x = y
The only single-digit values for x and y that satisfy the requirements are ...
x = 1, y = 8
The two-digit number of interest is 18.
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<em>Check</em>
Its sum of digits is 1+8 = 9. 2×9 = 18.
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<em>Comment on the relationship in the problem</em>
Many of us learned our multiplication tables for 9s by remembering that the sum of digits of 9n was 9, and that the leading digit of the product was n-1.
Answer:
1980
Step-by-step explanation:
It’s right, trust me
Answer:
He needs to order 
of carpet
Step-by-step explanation:
we know that
we have
Convert to 
Answer:
- $52
- this estimate is a little low
Explanation:
a) I might choose 6 1/2 hours and $8 per hour, so the estimated earnings would be ...
6(8) +(1/2)(8) = 52 dollars . . . . estimated earnings
These values are purposely chosen so that one is a little high and the other is a little low, hopefully producing a closer estimate than if both numbers were high (as 7 hours, $8, for example).
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b) Using 800 instead of 790 means the pay estimate is about 1/80 = 1.25% high.
Using 6 1/2 instead of 6 3/4 means the hours estimate is about 1/27 ≈ 3.7% low.
So, we expect the product of these values to be slightly low, perhaps by about 2.5%.
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<em>Comment on estimating</em>
If you can estimate the error in the estimate with some reasonable accuracy, you can use that to adjust the estimate to a pretty close value.
