1
00:00:00,000 --> 00:00:00,520


2
00:00:00,520 --> 00:00:02,840
Janelle is training
for a road race.

3
00:00:02,840 --> 00:00:06,090
Her pedometer tracks how
far she runs every day.

4
00:00:06,090 --> 00:00:08,350
Here are the pedometer readings
for the past four

5
00:00:08,350 --> 00:00:13,190
days: on Saturday, she went
3.89 miles; Sunday, 5.1;

6
00:00:13,190 --> 00:00:18,190
Monday, 10.21; Tuesday, 3.35.

7
00:00:18,190 --> 00:00:21,750
Estimate the total distance she
ran over the four days,

8
00:00:21,750 --> 00:00:23,640
and then calculate
the exact amount.

9
00:00:23,640 --> 00:00:26,460
Let's estimate first. So I'm
just going to round them to

10
00:00:26,460 --> 00:00:27,380
the nearest mile.

11
00:00:27,380 --> 00:00:30,190
So 3.89, let's round
it up to 4 miles.

12
00:00:30,190 --> 00:00:32,600
And I'm doing that because in
the tenths place, we have an

13
00:00:32,600 --> 00:00:34,730
8, which is 5 or greater.

14
00:00:34,730 --> 00:00:38,370
So let's just make that
roughly 4 miles.

15
00:00:38,370 --> 00:00:39,770
Let's make this 5.1.

16
00:00:39,770 --> 00:00:43,040
We round that down because
this 1 is less than 5.

17
00:00:43,040 --> 00:00:45,350
So let's make this 5 miles.

18
00:00:45,350 --> 00:00:50,960
10.21, let's make that
10 miles because

19
00:00:50,960 --> 00:00:51,950
2 would round down.

20
00:00:51,950 --> 00:00:53,480
It's less than 5.

21
00:00:53,480 --> 00:00:57,470
And 3.35, let's make that 3
miles, because 3 is less than

22
00:00:57,470 --> 00:00:58,740
5, so we'd round down.

23
00:00:58,740 --> 00:01:00,610
So that is 3 miles.

24
00:01:00,610 --> 00:01:04,090
And if we were to add them
up, 4 plus 5 is 9.

25
00:01:04,090 --> 00:01:07,110
9 plus 10 is 19.

26
00:01:07,110 --> 00:01:11,040
19 plus 3 is 22.

27
00:01:11,040 --> 00:01:20,040
So my estimate is that she ran
22 miles over the four days.

28
00:01:20,040 --> 00:01:21,080
That's my estimate.

29
00:01:21,080 --> 00:01:24,200
Now let's figure out the exact
amount that she ran.

30
00:01:24,200 --> 00:01:25,670
Let me scroll down
a little bit.

31
00:01:25,670 --> 00:01:32,940
So we're going to have to add
3.89 to 5.1-- and remember,

32
00:01:32,940 --> 00:01:34,870
when you're adding decimals,
you want to line up the

33
00:01:34,870 --> 00:01:44,390
decimal-- 10.21 and
then finally 3.35.

34
00:01:44,390 --> 00:01:47,900
And let's add all of these up.

35
00:01:47,900 --> 00:01:52,500
Now we'll start in the
hundredths place.

36
00:01:52,500 --> 00:01:56,820
There's nothing here, so 9 plus
nothing plus 1 is 10,

37
00:01:56,820 --> 00:01:59,340
plus 5 is 15.

38
00:01:59,340 --> 00:02:04,910
So let's write the 5, and then
carry, or regroup, the 1.

39
00:02:04,910 --> 00:02:06,360
Let me do this in
another color.

40
00:02:06,360 --> 00:02:10,030
1 plus 8 is 9.

41
00:02:10,030 --> 00:02:12,090
9 plus 1 is 10.

42
00:02:12,090 --> 00:02:14,190
10 plus 2 is 12.

43
00:02:14,190 --> 00:02:17,240
12 plus 3 is 15.

44
00:02:17,240 --> 00:02:18,750
Put the 5 down.

45
00:02:18,750 --> 00:02:21,045
Carry, or regroup, the 1.

46
00:02:21,045 --> 00:02:22,810
1 plus 3 is 4.

47
00:02:22,810 --> 00:02:25,140
4 plus 5 is 9.

48
00:02:25,140 --> 00:02:26,790
9 plus 0 is still 9.

49
00:02:26,790 --> 00:02:33,480
9 plus 3 is 12.

50
00:02:33,480 --> 00:02:33,960
Write the 2.

51
00:02:33,960 --> 00:02:35,800
Regroup this 1 right here.

52
00:02:35,800 --> 00:02:38,530
I'll do it out here just so it's
not part of any of these

53
00:02:38,530 --> 00:02:42,340
numbers, and then
1 plus 1 is 2.

54
00:02:42,340 --> 00:02:43,770
And then we have to remember
the decimal

55
00:02:43,770 --> 00:02:46,010
sitting right over there.

56
00:02:46,010 --> 00:02:52,760
So the exact distance she
ran was 22.55 miles.

57
00:02:52,760 --> 00:02:54,160
So our estimate wasn't
too bad.

58
00:02:54,160 --> 00:02:55,630
It was 22 miles.

59
00:02:55,630 --> 00:02:58,760
We got reasonably close, within
about little over a

60
00:02:58,760 --> 00:03:00,310
half a mile.

61
00:03:00,310 --> 00:03:00,799