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Donna is collecting stamps. On the first day, she collects 5. On the second day, she collects 9. Each day, she collects 4 more stamps than the day before. How many total stamps will she have after 20 days?

Respuesta :

Answer:

81 stamps

Step-by-step explanation:

Here we will use the AP formula

We know that

a_n = a + (n - 1)d

a = first term = 5

n = number of terms = 20

d = common difference = 9 - 5 = 4

On putting values

=> a_20 = 5 + (20 - 1)4

=> a_20 = 5 + (19)4

=> a_20 = 5 + 76

=> a_20 = 81

Therefore,

She will have 81 stamps after 20 days

[tex]\huge{\purple{\underline{\underline{\sf{\pink{ANSWER:-}}}}}}[/tex]

Here we have,

  • first term (a) = 5

  • no. of terms (n) = 20

  • common difference (d) = 9 - 5 = 4

[tex]\implies\tt{a_n = a + (n - 1) \times d} \\ \\ \implies\tt{a_20 = 5 + (20 - 1) \times 4} \\ \\ \implies\tt{a_20 = 5 + 19 \times 4} \\ \\ \implies\tt{a_20 = 5 + 76} \\ \\ \implies\tt{a_20 = 81}[/tex]

  • Hence, there will be 81 stamps after 20 days.
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