Round-off 108.76 to the nearest tens. Write sqrt(60) correct to four significant figures. You may use a calculator or a square-roots table of values. Evaluate and write your answer correct to two significant figures: 72+43= Estimate the product: 23.8 x 349

In the number 108.76, the tens digit is 0.

The digit to the right of 0 is 8 (in the ones place).

Since 8 is 5 or greater, round up the tens digit. The 0 becomes 1. All digits to the right of the tens place (before the decimal) become 0, and digits after the decimal are dropped.

The number rounded to the nearest tens is $\boxed{\mathbf{110}}$.

2. Write $\sqrt{60}$ correct to four significant figures.

Using a calculator, $\sqrt{60} \approx 7.74596669...$

The first four significant figures are 7, 7, 4, 5. The fifth significant figure is 9, which is 5 or greater, so we round up the fourth significant figure (5).

$\sqrt{60}$ correct to four significant figures is $\boxed{\mathbf{7.746}}$.

3. Evaluate $7^2 + 4^3$ and write your answer correct to two significant figures.

The first two significant figures are 1 and 1. The third significant figure is 3, which is less than 5, so we keep the second significant figure as it is and replace the remaining digits before the decimal with zeros.

The evaluated expression correct to two significant figures is $\boxed{\mathbf{110}}$.

4. Estimate the product: $23.8 \times 349$.

Round 23.8 to the nearest ten: $23.8 \approx 20$.
Round 349 to the nearest hundred: $349 \approx 300$.

The estimated product is $\boxed{\mathbf{6000}}$.