Which Two Power Cells Make 13? Grade 1 Number Bonds to 20

The reactor needs exactly thirteen units of power and there are more cells on the rack than will fit. Picking the pair that adds to the target is a missing-addend problem wearing a different coat: a first grader who knows 8 + 5 also has to notice that 9 + 4 gets there too, and that 8 + 4 does not. This is the station where addition stops being one question with one answer and becomes something you search through — which is exactly the flexibility first grade is aiming for.

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What this station asks for

⚛️ Restart the Reactor CoreThe lights are out. Tap the power cells that add up to exactly the target and slot them into the core — then watch it spin up and glow! You pick the power cells that add up to the exact target and restart the core. Five tasks, then a snack wrapper goes into the Case File.

Five questions it might ask

Drawn from the same pool the activity uses, so these are the real thing rather than an illustration. The numbers change on every attempt — there is no fixed set to memorize.

Question	Answer
Power the reactor to exactly 16	16
Power the reactor to exactly 12	12
Power the reactor to exactly 14	14
Power the reactor to exactly 17	17
Power the reactor to exactly 18	18

👀 What to watch for

Children who are secure with number facts can still stall here, because the question is inverted. If they're picking cells at random and checking, that's a reasonable first strategy — the shift you want is toward asking "thirteen take away eight leaves what?" before touching anything.

The Common Core standard behind it

Official wording, quoted in full — not our summary of it:

1.OA.C.6	Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten; decomposing a number leading to a ten; using the relationship between addition and subtraction; and creating equivalent but easier or known sums.

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Other Grade 1 skills in this case

Addition within 201.OA.C.6 Subtraction within 201.OA.C.6 Adding tens within 1001.NBT.C.4

All grades

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