Question: (4 x 10⁴)(2 x 10¹)
Answer:
Using the knowledge that a x 10ⁿ = a followed by ⁿ zeroes (eg: 5 x 10³ = 5,000)
We know that:
4 x 10⁴ is equal to 40,000
2 x 10¹ is equal to 20
Using the knowledge that (a)(b) = a x b, our next step would be to multiply those figures together.
40,000 x 20. We can do this without a calculator by counting how many zeroes are there.
Since there’s 5 zeroes, we know our answer will have 5 zeroes and we can take those 5 zeroes out of our equation:
So instead of 40000 x 20, we have 4 x 2 which we know is 8. Using our knowledge that our answer will have 5 zeroes, 40000 x 20 is equal to 800,000 (8 followed by 5 zeroes).
Our final step is to put that number into scientific notation. We know that 800,000 contains 5 zeroes, therefore 800,000 in scientific notation is:
8 x 10⁵
The correct answer would be D.
I hope this made sense and helps you and if you have any questions or think that I’ve made a mistake please let me know!
:)