Sara was thinking of a number. Sara divides by 2, then adds 10 to get an answer of 6. What was the original number?
2 answers:
Answer:
-8
Step-by-step explanation:
We know that Sara has a number by which she divides by 2, added 10 and ended up with 6. We are then asked to find the original number she had in mind.
To solve, we need to go backwards, starting with the original number, and applying all the steps she did but with the opposite operation.
6 is her ended number, we know before she added 10, so subtract 10 from 6:
Now we know that she divided by 2, therefore multiply -4 by 2:
-8 was Sara's first number.
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Answer:
2.4×10^6
Step-by-step explanation:
Put the numbers where the variables are and do the arithmetic. You can enter the numbers in scientific notation into your (scientific) calculator and have it show you the result in the same format.
r = (3.8×10^5)^2/(5.9×10^4) . . . . . denominator parentheses are required
Please note that in the above expression, parentheses are required around the denominator number. This is because it is a product of two numbers. In your pocket calculator or spreadsheet, you can enter that value as a single number (not a product). Parentheses are not required when you can do that.
r = (3.8²/5.9)×10^(5·2-4) ≈ 2.4×10^6
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The "exact" value is a repeating decimal with a long repeat. We have rounded to 2 significant digits here because the input numbers have that number of significant digits.
