UST Elementary Daily Math Challenge
Week 4 — Smart Calculation & Mental Math
September 7–13, 2026
50 Problems • Grades 3–5 Focus
A little math every day. A little stronger every week.
Weekly Format
每天完成一小部分；周末完成 Challenge
2
Monday: Questions 1–10
Tuesday: Questions 11–20
Wednesday: Questions 21–30
Thursday: Questions 31–40
Friday / Weekend: Questions 41–50 + Challenge
Goal: Think first, calculate second, and explain your reasoning.
Daily Practice
Questions 1–5
3
1. Which is a smart way to find 50+22? A) Add 1 to both B) Make 50 into 51, then subtract 1 C) Multiply D) Divide
2. Which is a smart way to find 51+23? A) Add 1 to both B) Make 51 into 52, then subtract 1 C) Multiply D) Divide
3. Which is a smart way to find 52+24? A) Add 1 to both B) Make 52 into 53, then subtract 1 C) Multiply D) Divide
4. Which is a smart way to find 53+25? A) Add 1 to both B) Make 53 into 54, then subtract 1 C) Multiply D) Divide
5. Which is a smart way to find 54+26? A) Add 1 to both B) Make 54 into 55, then subtract 1 C) Multiply D) Divide
Daily Practice
Questions 6–10
4
6. Which is a smart way to find 55+27? A) Add 1 to both B) Make 55 into 56, then subtract 1 C) Multiply D) Divide
7. Which is a smart way to find 56+28? A) Add 1 to both B) Make 56 into 57, then subtract 1 C) Multiply D) Divide
8. Which is a smart way to find 57+29? A) Add 1 to both B) Make 57 into 58, then subtract 1 C) Multiply D) Divide
9. Which is a smart way to find 58+30? A) Add 1 to both B) Make 58 into 59, then subtract 1 C) Multiply D) Divide
10. Which is a smart way to find 59+31? A) Add 1 to both B) Make 59 into 60, then subtract 1 C) Multiply D) Divide
Daily Practice
Questions 11–15
5
11. Which is a smart way to find 60+32? A) Add 1 to both B) Make 60 into 61, then subtract 1 C) Multiply D) Divide
12. Which is a smart way to find 61+33? A) Add 1 to both B) Make 61 into 62, then subtract 1 C) Multiply D) Divide
13. Which is a smart way to find 62+34? A) Add 1 to both B) Make 62 into 63, then subtract 1 C) Multiply D) Divide
14. Which is a smart way to find 63+35? A) Add 1 to both B) Make 63 into 64, then subtract 1 C) Multiply D) Divide
15. Which is a smart way to find 64+36? A) Add 1 to both B) Make 64 into 65, then subtract 1 C) Multiply D) Divide
Daily Practice
Questions 16–20
6
16. 198 + 27 = ___
17. 208 + 27 = ___
18. 218 + 27 = ___
19. 228 + 27 = ___
20. 238 + 27 = ___
Daily Practice
Questions 21–25
7
21. 248 + 27 = ___
22. 258 + 27 = ___
23. 268 + 27 = ___
24. 278 + 27 = ___
25. 288 + 27 = ___
Daily Practice
Questions 26–30
8
26. 298 + 27 = ___
27. 308 + 27 = ___
28. 318 + 27 = ___
29. 328 + 27 = ___
30. 338 + 27 = ___
Daily Practice
Questions 31–35
9
31. Maya has $51. She spends $19. How much remains?
32. Maya has $52. She spends $19. How much remains?
33. Maya has $53. She spends $19. How much remains?
34. Maya has $54. She spends $19. How much remains?
35. Maya has $55. She spends $19. How much remains?
Daily Practice
Questions 36–40
10
36. Maya has $56. She spends $19. How much remains?
37. Maya has $57. She spends $19. How much remains?
38. Maya has $58. She spends $19. How much remains?
39. Maya has $59. She spends $19. How much remains?
40. Maya has $60. She spends $19. How much remains?
Daily Practice
Questions 41–45
11
41. Maya has $61. She spends $19. How much remains?
42. Maya has $62. She spends $19. How much remains?
43. Maya has $63. She spends $19. How much remains?
44. Maya has $64. She spends $19. How much remains?
45. Maya has $65. She spends $19. How much remains?
Weekly Challenge
Questions 46–50
12
46. Challenge: Find 100 ÷ 25 mentally.
47. Challenge: Find 125 ÷ 25 mentally.
48. Challenge: Find 150 ÷ 25 mentally.
49. Challenge: Find 175 ÷ 25 mentally.
50. Challenge: Find 200 ÷ 25 mentally.
Answer Key — Questions 1–5
Answer + How to Solve
13
1. Answer: B
How to solve: Compensate: (51) + 22 − 1 gives the same sum and uses a round number.
2. Answer: B
How to solve: Compensate: (52) + 23 − 1 gives the same sum and uses a round number.
3. Answer: B
How to solve: Compensate: (53) + 24 − 1 gives the same sum and uses a round number.
4. Answer: B
How to solve: Compensate: (54) + 25 − 1 gives the same sum and uses a round number.
5. Answer: B
How to solve: Compensate: (55) + 26 − 1 gives the same sum and uses a round number.
Answer Key — Questions 6–10
Answer + How to Solve
14
6. Answer: B
How to solve: Compensate: (56) + 27 − 1 gives the same sum and uses a round number.
7. Answer: B
How to solve: Compensate: (57) + 28 − 1 gives the same sum and uses a round number.
8. Answer: B
How to solve: Compensate: (58) + 29 − 1 gives the same sum and uses a round number.
9. Answer: B
How to solve: Compensate: (59) + 30 − 1 gives the same sum and uses a round number.
10. Answer: B
How to solve: Compensate: (60) + 31 − 1 gives the same sum and uses a round number.
Answer Key — Questions 11–15
Answer + How to Solve
15
11. Answer: B
How to solve: Compensate: (61) + 32 − 1 gives the same sum and uses a round number.
12. Answer: B
How to solve: Compensate: (62) + 33 − 1 gives the same sum and uses a round number.
13. Answer: B
How to solve: Compensate: (63) + 34 − 1 gives the same sum and uses a round number.
14. Answer: B
How to solve: Compensate: (64) + 35 − 1 gives the same sum and uses a round number.
15. Answer: B
How to solve: Compensate: (65) + 36 − 1 gives the same sum and uses a round number.
Answer Key — Questions 16–20
Answer + How to Solve
16
16. Answer: 225
How to solve: Think 200+27-2 = 225.
17. Answer: 235
How to solve: Think 210+27-2 = 235.
18. Answer: 245
How to solve: Think 220+27-2 = 245.
19. Answer: 255
How to solve: Think 230+27-2 = 255.
20. Answer: 265
How to solve: Think 240+27-2 = 265.
Answer Key — Questions 21–25
Answer + How to Solve
17
21. Answer: 275
How to solve: Think 250+27-2 = 275.
22. Answer: 285
How to solve: Think 260+27-2 = 285.
23. Answer: 295
How to solve: Think 270+27-2 = 295.
24. Answer: 305
How to solve: Think 280+27-2 = 305.
25. Answer: 315
How to solve: Think 290+27-2 = 315.
Answer Key — Questions 26–30
Answer + How to Solve
18
26. Answer: 325
How to solve: Think 300+27-2 = 325.
27. Answer: 335
How to solve: Think 310+27-2 = 335.
28. Answer: 345
How to solve: Think 320+27-2 = 345.
29. Answer: 355
How to solve: Think 330+27-2 = 355.
30. Answer: 365
How to solve: Think 340+27-2 = 365.
Answer Key — Questions 31–35
Answer + How to Solve
19
31. Answer: $32
How to solve: Subtract 20, then add 1 back: 51-20+1=32.
32. Answer: $33
How to solve: Subtract 20, then add 1 back: 52-20+1=33.
33. Answer: $34
How to solve: Subtract 20, then add 1 back: 53-20+1=34.
34. Answer: $35
How to solve: Subtract 20, then add 1 back: 54-20+1=35.
35. Answer: $36
How to solve: Subtract 20, then add 1 back: 55-20+1=36.
Answer Key — Questions 36–40
Answer + How to Solve
20
36. Answer: $37
How to solve: Subtract 20, then add 1 back: 56-20+1=37.
37. Answer: $38
How to solve: Subtract 20, then add 1 back: 57-20+1=38.
38. Answer: $39
How to solve: Subtract 20, then add 1 back: 58-20+1=39.
39. Answer: $40
How to solve: Subtract 20, then add 1 back: 59-20+1=40.
40. Answer: $41
How to solve: Subtract 20, then add 1 back: 60-20+1=41.
Answer Key — Questions 41–45
Answer + How to Solve
21
41. Answer: $42
How to solve: Subtract 20, then add 1 back: 61-20+1=42.
42. Answer: $43
How to solve: Subtract 20, then add 1 back: 62-20+1=43.
43. Answer: $44
How to solve: Subtract 20, then add 1 back: 63-20+1=44.
44. Answer: $45
How to solve: Subtract 20, then add 1 back: 64-20+1=45.
45. Answer: $46
How to solve: Subtract 20, then add 1 back: 65-20+1=46.
Answer Key — Questions 46–50
Answer + How to Solve
22
46. Answer: 4
How to solve: Use the fact that 25 × 4 = 100, or recognize the multiple of 25.
47. Answer: 5
How to solve: Use the fact that 25 × 4 = 100, or recognize the multiple of 25.
48. Answer: 6
How to solve: Use the fact that 25 × 4 = 100, or recognize the multiple of 25.
49. Answer: 7
How to solve: Use the fact that 25 × 4 = 100, or recognize the multiple of 25.
50. Answer: 8
How to solve: Use the fact that 25 × 4 = 100, or recognize the multiple of 25.
Week Complete!
Think • Reason • Solve • Explain