Answer:
about 35
Explanation:
This question is asking for an estimate, which means you round the number(s) to something convenient to perform the calculation.
Here, 47% is conveniently rounded to 50% = 50/100 = 1/2. Then 1/2 of 70 is ...
1/2·70 = 70/2 = 35
A reasonable estimate of 47% of 70 is 35.
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As you get more sophisticated in your estimating, you can also estimate the error. This estimate is about 3% (of 70) high, so is high by 3/100·70 = 2.1. That means the real answer is 35 - 2.1 = 32.9.
You could also estimate the error as 3% of 100 = 3/100·100 = 3, so you could say the actual value is between 35-3 = 32 and 35. Since 100 is larger than 70, you know that 3% of 100 is larger than 3% of 70, so this is an over-estimate of the error.