1.
Aisha's lab printed 6 sheets of memory-cell labels with 145 labels on each sheet. 218 labels were used on the charts. How many labels are left?
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Answer:
Did you know? After you beat an infection, a few cells stay behind for years just to remember it. They are called memory cells.
2.
There are 196 memory cells to store. Each tube holds 8 cells. How many tubes are needed so that no cell is left out?
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Answer:
Did you know? Memory cells are why you usually catch chickenpox only once. Your body recognises it the second time and stops it early.
3.
A lab counted 187 memory cells in the morning and 233 in the afternoon. All of them are shared evenly across 6 racks. How many cells go on each rack?
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Answer:
Did you know? A vaccine works by teaching memory cells without you ever getting sick. It is a practice drill for your immune system.
4.
One vial is 5/6 full. Another vial is 3/4 full. Which vial holds more?
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Answer:
Did you know? Some memory cells live longer than you have been alive. Measles memory can last a whole lifetime.
5.
A rectangular storage tray has an area of 96 square centimetres. One side is 8 cm long. How long is the other side, and what is the perimeter of the tray?
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Answer:
Did you know? Your bone marrow, spleen and lymph nodes all store memory cells, so the record is kept in more than one place.
1.
Bilal weighs one memory-cell sample at 5.4 g and another at 2.75 g. What is their total weight, and how much heavier is the first sample than the second?
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Answer:
Did you know? Memory cells are rare — often fewer than one in a thousand of the cells in your blood — but they are the ones that end a repeat infection fast.
2.
A tray was 5/6 full of samples. 1/4 of a tray was used up in testing. What fraction of a tray is left?
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Answer:
Did you know? There are two kinds of memory cell. B cells remember how to build the antibody; T cells remember how to kill an infected cell.
3.
A cold store holds 58 racks, and each rack holds 34 vials. How many vials are in the store altogether?
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Answer:
Did you know? Samples like these are stored at about −80°C. That is colder than the coldest temperature ever recorded in Antarctica.
4.
A technician packs 2,617 memory cells into boxes that hold 6 each. How many boxes are completely full, and how many cells are left over?
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Answer:
Did you know? Your immune system can remember roughly a billion different germ shapes — without ever having met most of them.
5.
A counting machine logged 1,944 memory cells in 8 hours, at a steady rate. At that same rate, how many would it log in the next 5 hours? If those cells are loaded into trays of 8, how many trays are full and how many cells are left over?
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Answer:
Did you know? A booster shot works by finding the memory cells you already have and multiplying them, which is why the second dose acts faster than the first.
3rd Grade
1. 652 labels left.
145 × 6 = 870, then 870 − 218 = 652. Multiply first, subtract second.
2. 25 tubes.
196 ÷ 8 = 24 remainder 4. Those 4 spare cells still need a tube, so round up to 25. "24" is one step short.
3. 70 cells per rack.
187 + 233 = 420, then 420 ÷ 6 = 70. Add both parts of the day first, then split. Dividing 187 by 6 alone forgets the afternoon.
4. The 5/6 vial.
Twelfths: 5/6 = 10/12 vs 3/4 = 9/12, so 5/6 holds more — but only once the twelfths make them fair to compare.
5. Other side 12 cm; perimeter 40 cm.
96 ÷ 8 = 12 cm (the missing side). Perimeter = 2 × (8 + 12) = 40 cm. Gives area, asks perimeter — divide for the side, don't halve.
4th Grade
1. Total 8.15 g; the first is heavier by 2.65 g.
Write 5.4 as 5.40 and line up the points. 5.40 + 2.75 = 8.15; 5.40 − 2.75 = 2.65. Scaffold is off entirely today — the padding line is no longer printed, he has to write it himself.
2. 7/12 of a tray left.
Twelfths: 5/6 = 10/12, 1/4 = 3/12. 10/12 − 3/12 = 7/12. Unlike denominators, no scaffold, subtraction again.
3. 1,972 vials.
58 × 34 = (58 × 30) + (58 × 4) = 1,740 + 232 = 1,972. Two-by-two: the second partial row shifts one column left.
4. 436 full boxes, 1 cell left over.
2,617 ÷ 6 = 436 remainder 1. Check: 436 × 6 + 1 = 2,617. ✓ The question asks for both the full count and the leftover.
5. 1,215 cells — 151 full trays, 7 left over.
Rate first: 1,944 ÷ 8 = 243 per hour. Then 243 × 5 = 1,215. Then 1,215 ÷ 8 = 151 r 7. Check: 151 × 8 + 7 = 1,215. ✓