1.
Hamza loads 128 cell trays onto each of 4 carts. Later, 137 trays are sent out to the blood vessels. How many trays are still at the factory?
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Answer:
Did you know? Bone marrow is the soft, spongy middle of your bones. It is the factory where nearly every blood cell in your body is born.
2.
Aisha must pack 174 marrow samples. Each case holds 8 samples. How many cases are needed so that every sample is packed?
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Answer:
Did you know? Your marrow makes about two million red blood cells every single second â and it never takes a day off.
3.
Bilal logs 246 new cells in the morning and 354 in the afternoon. They are shared equally among 6 growth chambers. How many cells does each chamber hold?
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Answer:
Did you know? A red blood cell lives about four months, travelling your whole body over and over, before the spleen retires it.
4.
One marrow flask is 3/4 full. Another is 5/8 full. Which flask holds more? How do you know?
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Answer:
Did you know? Marrow is not all the same colour. Red marrow makes blood cells; yellow marrow stores fat and can switch back to red if your body needs it.
5.
A rectangular marrow tray has an area of 72 square cm. One side measures 9 cm. How long is the other side? What is the perimeter of the tray?
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Answer:
Did you know? As a baby, almost every bone you have makes blood. As you grow, the job moves mostly to your hips, ribs, spine and breastbone.
1. GUIDED
Zaynab weighs one marrow sample at 4.62 g and another at 3.9 g. What is their total weight, and how much heavier is the first sample than the second?
Pad the short one so the points line up: 3.9 becomes
Answer:
Did you know? A marrow sample is taken with a needle from the hip bone. The whole test takes about twenty minutes.
2.
One shelf holds 7/8 of a crate of vials. Another shelf holds 1/3 of a crate. How much more does the first shelf hold?
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Answer:
Did you know? Stem cells in your marrow are blank cells. They can become a red cell, a white cell, or a platelet, depending on what the body orders.
3.
Yaqub packs 47 vials into each of 36 cases. How many vials does he pack altogether?
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Answer:
Did you know? Platelets are the smallest blood cells. They rush to a cut and stick together to start the plug that becomes a scab.
4.
The factory ships 3,142 samples. Each crate holds 7. How many full crates are there, and how many samples are left over?
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Answer:
Did you know? A marrow donation does not remove bone. Donors usually give stem cells straight from the blood, and the marrow replaces them within weeks.
5.
A machine produced 2,184 cells in 6 hours. At that same rate, how many would it produce in 9 hours? Those cells are then packed into boxes of 8 â how many full boxes, and how many left over?
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Answer:
Did you know? If you laid out all the blood vessels your marrow supplies, they would stretch about 60,000 miles â more than twice around the Earth.
3rd Grade
1. 375 trays still at the factory.
128 × 4 = 512, then 512 − 137 = 375. Multiply first, subtract second.
2. 22 cases.
174 ÷ 8 = 21 remainder 6. Those 6 spare samples still need a case, so round up to 22. "21" is one step short.
3. 100 cells per chamber.
246 + 354 = 600, then 600 ÷ 6 = 100. Add both parts of the day first, then split. Dividing 246 by 6 alone forgets the afternoon.
4. The 3/4 flask.
Eighths: 3/4 = 6/8 vs 5/8, so 3/4 holds more â but only once the eighths make them fair to compare.
5. Other side 8 cm; perimeter 34 cm.
72 ÷ 9 = 8 cm (the missing side). Perimeter = 2 × (9 + 8) = 34 cm. Gives area, asks perimeter â divide for the side, don't halve.
4th Grade
1. Total 8.52 g; the first is heavier by 0.72 g.
Write 3.9 as 3.90 and line up the points. 4.62 + 3.90 = 8.52; 4.62 − 3.90 = 0.72. Scaffold is lighter than yesterday â only the padding line is printed now.
2. 13/24 of a crate more.
Twenty-fourths: 7/8 = 21/24, 1/3 = 8/24. 21/24 − 8/24 = 13/24. Unlike denominators, no scaffold, and a subtraction again.
3. 1,692 vials.
47 × 36 = (47 × 30) + (47 × 6) = 1,410 + 282 = 1,692. Two-by-two: the second partial row shifts one column left.
4. 448 full crates, 6 samples left over.
3,142 ÷ 7 = 448 remainder 6. Check: 448 × 7 + 6 = 3,142. ✓ The question asks for both the full count and the leftover.
5. 3,276 cells â 409 full boxes, 4 left over.
Rate first: 2,184 ÷ 6 = 364 per hour. Then 364 × 9 = 3,276. Then 3,276 ÷ 8 = 409 r 4. Check: 409 × 8 + 4 = 3,276. ✓