Answer:
After the 6th day, beginning with the 7th day, he is walking less than 0.5 km.
Step-by-step explanation:
To find a percent of a number, change the percent to a decimal and multiply by the number. To find 90% of a number, change 90% to a decimal and multiply by the number.
90% = 0.9
He first walks 1 km. The next day, he walks 90% of 1 km. To find 90% of 1 km, multiply 0.9 by 1 km. It is 0.9 km. For the next day, he walks 90% of 0.9 km, which is 0.9 * 0.9 km = 0.81 km. To find how much he walks each day, multiply what he walked on the previous day by 0.9.
Now you can find out how much he walks each day until you see he walks less than 0.5 km.
Day 1: 1 km
Day 2: 1 km * 0.9 = 0.9 km
Day 3: 0.9 km * 0.9 = 0.81 km
Day 4: 0.81 km * 0.9 = 0.729 km
Day 4: 0.729 km * 0.9 = 0.6561
Day 5: 0.6561 km * 0.9 = 0.59049 km
Day 6: 0.59049 km * 0.9 = 0.531441 km
Day 7: 0.531441 km * 0.9 = 0.4782969 km
On the 6th day, he is still walking more than 0.5 km, but by the 7th day, he is walking less than 0.5 km.
Answer: After the 6th day, beginning with the 7th day, he is walking less than 0.5 km.
