Express the following quantities as an ordinary decimal number:

a) The sun has a diameter of 1.392 * 10^6
I get 1392000.
b) 8.4*10^-6
I get 0.000084
Is this right

The first one is correct. The second one is incorrect. Your answer is 8.4 *10^-5

you have 8.4*10^-6; start where the decimal is and count six times to the left because you have a negative exponent. This means the number is smaller than 1. So to left of the decimal we have 8 and since we have
10^-6, we add five zeros to the left of 8. Now you can see that :
0.0000084 is six digits to the left of 4. This number is less than 1.

The sign of the exponent is really what's important. I wrote 10^-6, it is of course 8.4*10^-6 or 8.4E-6 (more convenient)

I hope this helps...

The diameter of the sun you have written correctly. The number of 8.4 x 10^-6 needs one more zero than you have; i.e., you have 4 zeros and you need five.

To express a number written in scientific notation as an ordinary decimal number, you follow a few steps:

a) The sun has a diameter of 1.392 * 10^6.

To express this number as an ordinary decimal, you can simply remove the exponent and move the decimal point accordingly. The exponent tells us how many places to move the decimal point.
In this case, the exponent is 6, and it is positive. So, we move the decimal point 6 places to the right.
Starting with 1.392, we move the decimal point six places to the right and add zeros as needed:
1.392 * 10^6 = 1,392,000

So, the diameter of the sun expressed as an ordinary decimal number is 1,392,000.

b) 8.4*10^-6.

To express this number as an ordinary decimal, you need to move the decimal point according to the exponent.
In this case, the exponent is -6, and it is negative. So, we move the decimal point 6 places to the left.
Starting with 8.4, we move the decimal point six places to the left and add zeros as needed:
8.4 * 10^-6 = 0.0000084

So, the number 8.4*10^-6 expressed as an ordinary decimal number is 0.0000084.

I hope this explanation helps you understand how to express numbers in scientific notation as ordinary decimals.