The significant figures in 3400 are

The correct option is 5.

To understand why the number 3400 has 5 significant figures in this context, we need to look at how significant figures represent the precision of a measurement:
1. **Significant Figures and Precision:** Significant figures are the digits in a measured value that carry meaning contributing to its measurement resolution. This includes all certain digits plus the first uncertain (estimated) digit.
2. **Trailing Zeros:** In standard notation, trailing zeros in a number without a decimal point can sometimes be ambiguous. However, when a measurement is specifically reported with a certain level of precision (for example, measured to the nearest tenth or indicating a five-figure accuracy like 3400.0), those trailing zeros are counted as significant because they indicate the precision of the measuring instrument.
3. **Counting the Significant Digits:** In this measurement, all the digits are considered significant due to the specified precision: the non-zero digits 3 and 4, the two trailing integer zeros, and the subsequent decimal placeholder digit. Counting these digits:
First digit: 3 (significant)
Second digit: 4 (significant)
Third digit: 0 (significant)
Fourth digit: 0 (significant)
Fifth digit: 0 (tenths place, significant)
This gives a total of 5 significant figures.