When estimating a quotient, you can round the divisor AND dividend to a more simple division problem. Choose numbers that are close to each, but can be easily divided through more basic multiplication. Ex. 358 divided by 8, is easier viewed as 360 divided by 9, since 9 is easily divided into 36 evenly.
Explanation: The fleas and lice were the ones who infected the rats, then the fleas on the rat then bit humans which caused them to get infected with the plaque as well
