place value and powers of 10
what is the value of 7 in 47,325?
7,000
24 x 3
72
estimate 23 x 18
20 x 20 = 400
which answer is reasonable for 50 x 20
A. 100
B. 1,000
C. 10,000
B. 1,000
explain why would we round 23 x 18 to 20 x 20?
20 x 20 is easier to estimate
what is 34 x 100
3,400
32 x 20
640
estimate 456 x 42
500 x 40 = 20,000
a student says 597 x 52 = 600 x 50 =3000
is the estimate reasonable?
no. 600 x 50= 30,000
i rounded 456 to 500 because..
depends on answer given
what is 52 x 1,000
52,000
46 x 12
552
1,320 x 88
1,300 x 90 = 117,000
which expression would have a product closest to 200,000?
A. 2,146 x 12
B. 221,467 x 121
C. 2,146 x 121
D. 21, 477 x 1,217
C. 2,146 x 121
i always have to round both factors when I estimate. Is this true?
which is greater? 45 x100 or 450 x 10
they are both equal at 4,500
125 x 24
3, 000
13,205 x 880=
10,000 x 900 = 9,000, 000
two students estimate: 456 x 42
Student A 500 x 40 =20,000
Student B 400 x 40 = 16,000
both are reasonable!
500 x 40 = 20,000
Explain why this is true and you cant say I added zeroes
5 hundreds x 4 tens = 20 thousands
5 x 100 x 4 x 10
5 x 4 x 100 x 10
20 x 1000
when i multiply 36 x 100, i just add two zeroes. is that a good way to explain what happens? explain place value pattern.
the digit shifts two places to the left making the value 100 times greater. the two zeros are a result of that place value shift.
234 x 16
3,744
which is the better estimate for 5,840 x 25
A. 10,000
B. 150,000
C. 1,500,000
B. 150,000
put in order from smallest to largest
A. 4560 x 42
B. 4560 x 420
C. 456 x 42
C - A - B
a student says.... my estimate is different from yours so one of us must be wrong.
How would you respond?
different estimates can be reasonable.