To calculate simple interest, you first need to multiply the original amount by the percentage of the money which is going to be added.
In this situation, 500 x 0.05 is the interest which will be added each year.
Therefore, $25 will be added each year. Since it is over 4 years, it is (25*4).
So the account will have earned $100 of simple interest.
Although the account will contain $600, it will have EARNED $100 of interest since it started with $500 already.
Answer - A $100 of simple interest will be earned.
It typically just needs two parts
1) all parties must be in agreement
2) something of value needs to be exchanged. ie. money, a service
I would estimate 643 - 189 by rounding 643 to the tens place and 189 to the hundreds place.
643 => 640
189 => 200
Now you can subtract 200 from 640.
640 - 200 = 440
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