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Problem solving and the year in review

الأسبوع 29 · حل المسائل ومراجعة العام · 3 دروس
1

Choose add or take away

Discover Mathematics P2: Term 2, Lessons 111–120
GoalDecide whether a story problem needs adding, taking away, or comparing, then solve it.
New words
altogether · all the amounts put togetherleft · what remains after some are taken awaycompare · find how many more or fewernumber sentence · numbers and signs that tell the story
Explanation

Read the story slowly and ask what is happening. If things are put together or more arrive, add. If some are given away, eaten, sold or lost and we ask what is left, take away. If we ask how many more or how many fewer, compare by subtracting the smaller number from the bigger. Then write a number sentence, solve it, and check that the answer makes sense.

ClueWhat to do
in all, altogether, more comeadd
left, gave away, sold, losttake away
how many more, how many fewersubtract to compare
Worked examples
235128?
Hana has 235 stamps. She gets 128 more. How many stamps in all? More arrive, so add: 235 + 128 = 363 stamps.
175?450
A shop had 450 notebooks and sold 175. How many are left? Some were sold, so take away: 450 − 175 = 275 notebooks.
Seif120Omar85
Seif has 120 stickers and Omar has 85. How many more has Seif? Compare: 120 − 85 = 35 more stickers.
Class activity

Story swap. Each person writes three short stories with numbers up to 200: one that needs adding, one that needs taking away and one that compares. Swap papers. Solve each story and underline the clue words. Check each answer by doing the opposite operation.

Practice
1
There are 56 children in the yard and 38 more come. How many children are there in all?
2
A baker made 300 rolls and sold 145. How many are left?
3
Mariam has 72 beads and Jana has 49. How many more beads does Mariam have?
4
A bus carries 48 passengers. 19 get off. How many stay on the bus?
5
Mina read 24 pages on Monday and 37 pages on Tuesday. How many pages in all? Which sign did you use?