A man walks 20km in 4 hours. Find his speed.

5 km per hour

Explanation: If you set up a unit rate, you can simplify to find the answer.

20 km               ?

  =

4 hr                 1 hr

Use the crisscross method, so 20 times 1 is 20, and 20 divided by 4 is 5, so the answer is 5 km per one hour.

when it's short and dry.

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.