4. A student performed an experiment to determine the density of a sugar solution and obtainedthe following results: 1.24 g/mL, 1.21 g/mL, 1.23 g/mL. The actual density is 1.50 g/mL. Circle the correct value for the average, X, in the first column and for the accuracy evaluation, RE(%), in the second column.

1.23 g/mL

-18.2%

Explanation:

We need to find the average, which is just the sum of the numbers divided by the number of numbers. Here, the sum will be 1.24 + 1.21 + 1.23 = 3.68 g/mL. There are 3 numbers, so divide 3.68 by 3: 3.68 / 3 ≈ 1.2266...

However, we need to round this and take into account significant figures. Each trial gave a number with 3 significant figures, so we round our number off to three: 1.22666... ≈ 1.23. So, circle the first number under the X column.

We now need to find the percent error, which is RE (%). To calculate this, we take the measured value (1.23 in this case) and subtract the exact value (1.50 here) from it, and then divide that by the exact value:

(1.23 - 1.50) / 1.50 ≈ -0.1822...

Again, we need to round to 3 significant figures, which would make it:

-0.1822... ≈ -0.182

Thus, circle the last number under the RE (%) column.