Adding and subtracting (age 9+)
Solve addition and subtraction multi-step problems in contexts, deciding which operations and methods to use and why
کارهایی که یادگیرنده بعد از این درس می‌تواند انجام دهد
- A school collects 12,450 bottles in Week 1 and 8,372 in Week 2; their target is 25,000. How many more do they need?
- Choose between mental and written methods for each step and explain why
- Solve a three-step problem involving addition and subtraction of five-digit numbers
۱ · بخوان
Some problems take more than two steps to solve. Read the story slowly, one part at a time. At each step, ask yourself: am I adding or subtracting here? And should I work it out in my head, or write it down? Mentally, turn 46 minus 19 into 46 minus 20, then add 1 back. On paper, line up the columns, start from the ones place, and borrow when the top digit is smaller. Build the biggest tens digit, subtract the smallest digit.
A school collects 12,450 bottles in Week 1 and 8,372 in Week 2. Their target is 25,000 bottles. Step 1: add the two weeks. 12,450 + 8,372 = 20,822. That's a big sum with regrouping, so it helps to write it in columns. Step 2: subtract from the target. 25,000 minus 20,822 = 4,178. The school still needs 4,178 more bottles.
Look at the numbers before you pick a method. Round, simple numbers like 500 and 120 are quick to work out in your head. Numbers with several digits, or ones that need regrouping, are easier to get right on paper.
A class is raising money for a trip. They start with 15,000 pounds saved. Step 1: a bake sale raises 12,500 pounds. 15,000 + 12,500 = 27,500. That's easy to do in your head because both numbers are round. Step 2: they spend 8,750 pounds on bus tickets. 27,500 minus 8,750 = 18,750. This one is easier to write down, because of the regrouping. Step 3: they spend 3,200 pounds on entry tickets. 18,750 minus 3,200 = 15,550. No regrouping is needed, so mental works fine. The class has 15,550 pounds left.
Break a multi-step problem into stages, decide add or subtract at each one, and choose mental or written based on how tricky the numbers are.
۲ · ببین
به انگلیسیدور از صفحه‌نمایش
جایگاه این موضوع
اول این‌ها را یاد بگیر
پیوندهای اختیاری
این موضوع راه این‌ها را باز می‌کند
این موضوع به کجا می‌رسد
شغل‌هایی که بر این مهارت تکیه دارند. دنبال کردن یکی برای دیدن همهٔ چیزهایی که بر آن‌ها بنا شده است.
۱۱ سؤال پشت این درس منتظرند، هر کدام با پاسخ توضیح‌داده‌شده. هر پاسخ آسمان را پر می‌کند: ستاره‌ها هنگام یادگیری روشن می‌شوند و وقتی زمان برگشتن است کمرنگ می‌شوند.