به انگلیسی

Fast ways to add and subtract

ریاضی · جمع و تفریق · سن ۸ تا ۹ سال

نام ______________________ تاریخ ____________

Which equation has the same value on both sides?
- 360 + 220 = 900 - 310
- 430 + 150 = 800 - 210
- 470 + 120 = 800 - 210
- 520 + 140 = 900 - 250
To add 297 + 145, you replace 297 with 300. How do you adjust the total?
- Add 300 + 145, then subtract 3 from the total
- Add 300 + 145, then add 3 more to the total
- Add 300 + 145, then leave the total unchanged
Why does 500 + 287 need no regrouping?
- Both numbers have three digits, so no regrouping is needed
- Adding each place gives less than 10 in that place
- The total is odd, so no regrouping is needed in any place
Using place-value columns for 634 - 275 requires exchanging a ten and then a hundred.
دور یکی دایره کشیدن: درست نادرست
Which addition has an addend just 1 below a hundred, so you can round it up and subtract 1 from the total?
- 256 + 371
- 418 + 263
- 199 + 342
You found 426 + 185 = 611. Which subtraction checks this sum?
- 426 - 185 = 241
- 611 - 185 = 426
- 611 - 426 = 175
- 611 - 185 = 436
Use place-value columns to add 468 + 257. Type the total.
پاسخ: ______________
Use rounding and adjusting to add 396 + 258. Type the total.
پاسخ: ______________
Use the digits 2, 4, 6, 7, 8 and 9 exactly once across two three-digit numbers. Which subtraction gives the greatest difference?
- 984 - 267
- 976 - 248
- 974 - 268
- 987 - 246
Priya got 342 for 723 - 465 by subtracting the smaller digit from the larger digit in each column. Which repair gives the correct difference?
- Add the two numbers instead; the result is 1188
- Keep the order and regroup; the result is 258
- Reverse the digit subtractions; the result is 342

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470 + 120 = 800 - 210 · 470 + 120 and 800 - 210 both equal 590. The other equations have different values on their two sides.
Add 300 + 145, then subtract 3 from the total · Replacing 297 with 300 adds 3 extra. Since 300 + 145 = 445, subtract 3 to get the exact total, 442.
Adding each place gives less than 10 in that place · The place totals are 7 ones, 8 tens and 7 hundreds. None reaches 10, so no exchange is needed. The sum is 787.
درست · Exchange a ten to subtract 5 ones. Then exchange a hundred to subtract 7 tens. The difference is 359.
199 + 342 · 199 is 1 below 200. Calculate 200 + 342 = 542, then subtract the extra 1 to get 541.
611 - 185 = 426 · Subtract an addend from the total. 611 - 185 = 426 returns the other addend, so it checks the sum.
725 · 15 ones make 1 ten and 5 ones. The tens then total 12, making 1 hundred and 2 tens. The sum is 725.
654 · Add 4 to round 396 up to 400. Then 400 + 258 = 658. Subtract the extra 4 to get 654.
987 - 246 · Make the largest top number, 987, and the smallest bottom number, 246. Their difference is 741.
Keep the order and regroup; the result is 258 · Reversing the digit subtractions gives 342 but changes the calculation. Keep the order and exchange place-value parts to get 258.