This document contains 5 math problems involving multiplication and distribution. The first 3 problems ask the student to calculate expressions like 23 × 102, 15 × 98, and 12 × 99. The next problem asks the student to calculate 23 × 8.5 + 23 × 1.5. The final problem is 4.25 × 12 - 4.25 × 2. The second half of the document shows the step-by-step workings and solutions to each of the 5 problems.

1. Calcul mental
N°13
“développer et factoriser”

2. Diapositive 1Diapositive 1
23 × 102

4. Diapositive 2Diapositive 2
15 × 98

6. Diapositive 3Diapositive 3
12 × 99

8. 23×8,5 + 23×1,5
Diapositive 4Diapositive 4

10. 4,25×12–4,25×2
Diapositive 5Diapositive 5

12. FIN

13. CORRECTION

14. Diapositive 1Diapositive 1
23 × 102 = 23 × (100+2)
= 23 × 100 + 23 × 2
= 2300 + 46 = 2346

15. 15 × 98 = 15 × (100 - 2)
= 15 × 100 - 15 × 2
= 1500 - 30 = 1470
Diapositive 2Diapositive 2

16. 12 × 99 = 12 × (100 - 1)
= 12 × 100 - 12 × 1
= 1200 – 12 = 1188
Diapositive 3Diapositive 3

17. 23 × 8,5 + 23 × 1,5
= 23 × (8,5 + 1,5)
= 23 × 10 = 230
Diapositive 4Diapositive 4

18. 4,25 × 12 – 4,25 × 2
= 4,25 × (12 - 2)
= 4,25 × 10 = 42,5
Diapositive 5Diapositive 5