Which change(in percent) is bigger :
losing weight from 100 lb to 90 lb or losing weight from 50 lb to 40 lb ?

Losing weight from 50lb to 40lb is a larger percent change.

That would be the equivalent of going from 100lb to 80lbs

Step-by-step explanation:

the 8 in 8,420 is in the thousands place so it's value is 8 thousand.

the 8 in 6,870 is in the hundreds place so it's value is 8 hundred.

divide 8000 by 800 to find the answer:

8000 / 800 = 10

the 8 in 8,420 is 10 times greater than the 8 in 6,870