Addition and Subtraction to 10,000
Addition and subtraction to 10,000 extend the strategies from Grade 3 to four-digit numbers. Decompose 6,847 + 2,365 into thousands, hundreds, tens, and ones, add each independently, then recombine: 8,000 + 1,100 + 11 + 12 = 9,212 (with regrouping). The same place-value logic applies; the numbers are simply larger. Estimation becomes more critical as numbers grow larger, because errors are harder to spot without a predicted target.
Decompose by place value
6,847 + 2,365: thousands: 6000+2000=8000. Hundreds: 800+300=1100. Tens: 40+60=100. Ones: 7+5=12. Combine: 8000+1100+100+12 = 9212. Regrouping: 1100 = 1 thousand + 100, so adjust: 9000+200+12 = 9212. The process is identical to Grade 3 three-digit addition but with an extra place value position.
Friendly numbers for large values
7,994 + 3,256: 7,994 is close to 8,000 (add 6). 8,000 + 3,256 = 11,256. Subtract the 6 added: 11,256 - 6 = 11,250. Compensation works identically for large numbers. For subtraction: 9,003 - 4,998. 4,998 is close to 5,000. 9,003 - 5,000 = 4,003. Add back 2: 4,003 + 2 = 4,005.
Real-world contexts and number talks
Fish stocks in lakes: a lake had 8,450 fish. After a season, 1,230 were caught. How many remain? This is a subtraction problem with four-digit numbers in an ecologically meaningful context (BC curriculum explicitly references fish stocks). Number talks remain the most powerful pedagogical tool for developing flexible computation strategies.