0:00:00.000,0:00:00.520 0:00:00.520,0:00:02.840 Janelle is training[br]for a road race. 0:00:02.840,0:00:06.090 Her pedometer tracks how[br]far she runs every day. 0:00:06.090,0:00:08.350 Here are the pedometer readings[br]for the past four 0:00:08.350,0:00:13.190 days: on Saturday, she went[br]3.89 miles; Sunday, 5.1; 0:00:13.190,0:00:18.190 Monday, 10.21; Tuesday, 3.35. 0:00:18.190,0:00:21.750 Estimate the total distance she[br]ran over the four days, 0:00:21.750,0:00:23.640 and then calculate[br]the exact amount. 0:00:23.640,0:00:26.460 Let's estimate first. So I'm[br]just going to round them to 0:00:26.460,0:00:27.380 the nearest mile. 0:00:27.380,0:00:30.190 So 3.89, let's round[br]it up to 4 miles. 0:00:30.190,0:00:32.600 And I'm doing that because in[br]the tenths place, we have an 0:00:32.600,0:00:34.730 8, which is 5 or greater. 0:00:34.730,0:00:38.370 So let's just make that[br]roughly 4 miles. 0:00:38.370,0:00:39.770 Let's make this 5.1. 0:00:39.770,0:00:43.040 We round that down because[br]this 1 is less than 5. 0:00:43.040,0:00:45.350 So let's make this 5 miles. 0:00:45.350,0:00:50.960 10.21, let's make that[br]10 miles because 0:00:50.960,0:00:51.950 2 would round down. 0:00:51.950,0:00:53.480 It's less than 5. 0:00:53.480,0:00:57.470 And 3.35, let's make that 3[br]miles, because 3 is less than 0:00:57.470,0:00:58.740 5, so we'd round down. 0:00:58.740,0:01:00.610 So that is 3 miles. 0:01:00.610,0:01:04.090 And if we were to add them[br]up, 4 plus 5 is 9. 0:01:04.090,0:01:07.110 9 plus 10 is 19. 0:01:07.110,0:01:11.040 19 plus 3 is 22. 0:01:11.040,0:01:20.040 So my estimate is that she ran[br]22 miles over the four days. 0:01:20.040,0:01:21.080 That's my estimate. 0:01:21.080,0:01:24.200 Now let's figure out the exact[br]amount that she ran. 0:01:24.200,0:01:25.670 Let me scroll down[br]a little bit. 0:01:25.670,0:01:32.940 So we're going to have to add[br]3.89 to 5.1-- and remember, 0:01:32.940,0:01:34.870 when you're adding decimals,[br]you want to line up the 0:01:34.870,0:01:44.390 decimal-- 10.21 and[br]then finally 3.35. 0:01:44.390,0:01:47.900 And let's add all of these up. 0:01:47.900,0:01:52.500 Now we'll start in the[br]hundredths place. 0:01:52.500,0:01:56.820 There's nothing here, so 9 plus[br]nothing plus 1 is 10, 0:01:56.820,0:01:59.340 plus 5 is 15. 0:01:59.340,0:02:04.910 So let's write the 5, and then[br]carry, or regroup, the 1. 0:02:04.910,0:02:06.360 Let me do this in[br]another color. 0:02:06.360,0:02:10.030 1 plus 8 is 9. 0:02:10.030,0:02:12.090 9 plus 1 is 10. 0:02:12.090,0:02:14.190 10 plus 2 is 12. 0:02:14.190,0:02:17.240 12 plus 3 is 15. 0:02:17.240,0:02:18.750 Put the 5 down. 0:02:18.750,0:02:21.045 Carry, or regroup, the 1. 0:02:21.045,0:02:22.810 1 plus 3 is 4. 0:02:22.810,0:02:25.140 4 plus 5 is 9. 0:02:25.140,0:02:26.790 9 plus 0 is still 9. 0:02:26.790,0:02:33.480 9 plus 3 is 12. 0:02:33.480,0:02:33.960 Write the 2. 0:02:33.960,0:02:35.800 Regroup this 1 right here. 0:02:35.800,0:02:38.530 I'll do it out here just so it's[br]not part of any of these 0:02:38.530,0:02:42.340 numbers, and then[br]1 plus 1 is 2. 0:02:42.340,0:02:43.770 And then we have to remember[br]the decimal 0:02:43.770,0:02:46.010 sitting right over there. 0:02:46.010,0:02:52.760 So the exact distance she[br]ran was 22.55 miles. 0:02:52.760,0:02:54.160 So our estimate wasn't[br]too bad. 0:02:54.160,0:02:55.630 It was 22 miles. 0:02:55.630,0:02:58.760 We got reasonably close, within[br]about little over a 0:02:58.760,0:03:00.310 half a mile. 0:03:00.310,0:03:00.799