1st Grade Math Flashcards: Add Within 100

What this deck covers

This deck focuses on Add Within 100, giving you a quick way to review the definitions, rules, and examples that matter most for 1st Grade Math.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the sum of $29 + 10$?

Answer: $39$. Add tens: $20 + 10 = 30$, add ones: $9$, so $30 + 9 = 39$.

Flashcard 2: What is the sum of $65 + 20$?

Answer: $85$. Add tens: $60 + 20 = 80$, add ones: $5$, so $80 + 5 = 85$.

Flashcard 3: What is the sum of $57 + 20$?

Answer: $77$. Add tens: $50 + 20 = 70$, keep ones: $7$, so $77$.

Flashcard 4: What does it mean to "compose a ten" when adding within $100$?

Answer: Trade $10$ ones for $1$ ten. When ones sum to $10$ or more, regroup as $1$ ten.

Flashcard 5: What is the sum of $76 + 10$?

Answer: $86$. Add tens: $70 + 10 = 80$, add ones: $6$, so $80 + 6 = 86$.

Flashcard 6: What is the sum of $18 + 50$?

Answer: $68$. Add tens: $10 + 50 = 60$, add ones: $8$, so $60 + 8 = 68$.

Flashcard 7: What is the sum of $69 + 4$?

Answer: $73$. Add ones: $9 + 4 = 13$, compose a ten: $60 + 13 = 73$.

Flashcard 8: What is the sum of $84 + 5$?

Answer: $89$. Add ones: $4 + 5 = 9$, keep tens: $80$, so $89$.

Flashcard 9: What is the sum of $73 + 10$?

Answer: $83$. Add $10$ to the tens place: $70 + 10 = 80$, keep ones as $3$.

Flashcard 10: Identify the missing number: $52 + \square = 60$.

Answer: $8$. Count up from $52$ to $60$: need $8$ more.

Flashcard 11: What is the sum of $19 + 7$?

Answer: $26$. Add ones: $9 + 7 = 16$, regroup to get $26$.

Flashcard 12: What is the sum of $88 + 9$?

Answer: $97$. Add ones: $8 + 9 = 17$, compose a ten: $80 + 17 = 97$.

Flashcard 13: Which place values do you add first in $2$-digit addition: tens or ones?

Answer: Ones. Start with ones place to check if regrouping is needed.

Flashcard 14: What is the sum of $26 + 40$?

Answer: $66$. Add tens: $20 + 40 = 60$, keep ones: $6$, so $66$.

Flashcard 15: Identify the missing number: $37 + 3 = \square$.

Answer: $40$. Add ones: $7 + 3 = 10$, compose a ten: $30 + 10 = 40$.

Flashcard 16: What is the sum of $35 + 6$?

Answer: $41$. Add ones: $5 + 6 = 11$, compose a ten: $30 + 11 = 41$.

Flashcard 17: What is the missing addend in $58 + \square = 65$?

Answer: $7$. Find what adds to $8$ to make $15$ (ones become $5$, carry $1$).

Flashcard 18: What is the sum of $38 + 4$ using tens and ones?

Answer: $42$. Add ones to ones: $8 + 4 = 12$, compose a ten to get $40 + 2$.

Flashcard 19: What is the sum of $41 + 30$?

Answer: $71$. Add tens: $40 + 30 = 70$, keep ones: $1$, so $71$.

Flashcard 20: Identify the missing number: $\Box + 50 = 73$.

Answer: $23$. Subtract: $73 - 50 = 23$ to find the missing number.

Flashcard 21: What is the sum of $34 + 5$?

Answer: $39$. Add ones: $4 + 5 = 9$, keep tens: $30$, so $30 + 9 = 39$.

Flashcard 22: What is the sum of $62 + 30$ (add tens to tens)?

Answer: $92$. Add tens to tens: $60 + 30 = 90$, keep ones as $2$.

Flashcard 23: What is the sum of $32 + 40$?

Answer: $72$. Add tens: $30 + 40 = 70$, add ones: $2$, so $70 + 2 = 72$.

Flashcard 24: What is the sum of $37 + 6$?

Answer: $43$. Add ones: $7 + 6 = 13$, regroup to get $43$.

Flashcard 25: Identify the missing number: $36 + \Box = 40$.

Answer: $4$. Find what adds to $6$ to make $10$: it's $4$.

Flashcard 26: What is the missing addend in $36 + \square = 40$?

Answer: $4$. Find what adds to $6$ to make $10$ (ones place).

Flashcard 27: What is the sum of $58 + 7$?

Answer: $65$. Add ones: $8 + 7 = 15$, regroup to get $65$.

Flashcard 28: What is the sum of $67 + 9$?

Answer: $76$. Add ones: $7 + 9 = 16$, regroup to get $76$.

Flashcard 29: What is the sum of $27 + 9$?

Answer: $36$. Add ones: $7 + 9 = 16$, compose a ten: $20 + 16 = 36$.

Flashcard 30: What is the sum of $27 + 9$ (compose a ten if needed)?

Answer: $36$. Add ones: $7 + 9 = 16$, compose a ten to get $30 + 6$.

Flashcard 31: What is the sum of $58 + 6$ (compose a ten if needed)?

Answer: $64$. Add ones: $8 + 6 = 14$, compose a ten to get $60 + 4$.

Flashcard 32: What is the sum of $46 + 8$?

Answer: $54$. Add ones: $6 + 8 = 14$, regroup to get $54$.

Flashcard 33: What is the sum of $62 + 8$?

Answer: $70$. Add ones: $2 + 8 = 10$, regroup to get $70$.

Flashcard 34: What is the sum of $48 + 2$ (compose a ten)?

Answer: $50$. Add ones: $8 + 2 = 10$, compose a ten to get $50$.

Flashcard 35: What is the sum of $45 + 20$ (add a multiple of $10$)?

Answer: $65$. Add tens to tens: $40 + 20 = 60$, keep ones as $5$.

Flashcard 36: What is the sum of $39 + 1$ (compose a ten)?

Answer: $40$. Add ones: $9 + 1 = 10$, compose a ten to get $40$.

Flashcard 37: What is the sum of $67 + 5$?

Answer: $72$. Add ones to ones: $7 + 5 = 12$, compose a ten to get $70 + 2$.

Flashcard 38: What is the sum of $29 + 50$?

Answer: $79$. Add tens to tens: $20 + 50 = 70$, keep ones as $9$.

Flashcard 39: What is the sum of $73 + 20$?

Answer: $93$. Add tens: $70 + 20 = 90$, keep ones: $3$, so $93$.

Flashcard 40: What is the sum of $90 + 7$?

Answer: $97$. Add ones: $0 + 7 = 7$, keep tens: $90$, so $97$.

Flashcard 41: What is the sum of $39 + 40$?

Answer: $79$. Add tens: $30 + 40 = 70$, keep ones: $9$, so $79$.

Flashcard 42: What is the sum of $19 + 6$?

Answer: $25$. Add ones: $9 + 6 = 15$, compose a ten: $10 + 15 = 25$.

Flashcard 43: What is the sum of $48 + 30$?

Answer: $78$. Add tens: $40 + 30 = 70$, keep ones: $8$, so $78$.

Flashcard 44: What is the sum of $41 + 8$?

Answer: $49$. Add ones to ones: $1 + 8 = 9$, keep tens as $40$.

Flashcard 45: What is the sum of $24 + 60$?

Answer: $84$. Add tens to tens: $20 + 60 = 80$, keep ones as $4$.

Flashcard 46: What is the sum of $29 + 6$?

Answer: $35$. Add ones: $9 + 6 = 15$, regroup to get $35$.

Flashcard 47: What is the sum of $55 + 10$?

Answer: $65$. Add tens: $50 + 10 = 60$, keep ones: $5$, so $65$.

Flashcard 48: What is the sum of $46 + 7$?

Answer: $53$. Add ones to ones: $6 + 7 = 13$, compose a ten to get $50 + 3$.

Flashcard 49: What is the sum of $19 + 8$ (compose a ten)?

Answer: $27$. Add ones: $9 + 8 = 17$, compose a ten to get $20 + 7$.

Flashcard 50: What is the sum of $18 + 60$?

Answer: $78$. Add tens: $10 + 60 = 70$, keep ones: $8$, so $78$.

Flashcard 51: What is the sum of $47 + 30$?

Answer: $77$. Add tens: $40 + 30 = 70$, add ones: $7$, so $70 + 7 = 77$.

Flashcard 52: What is the sum of $55 + 9$ (compose a ten if needed)?

Answer: $64$. Add ones: $5 + 9 = 14$, compose a ten to get $60 + 4$.

Flashcard 53: What is the sum of $48 + 3$?

Answer: $51$. Add ones: $8 + 3 = 11$, compose a ten: $40 + 11 = 51$.