+10

11 months ago

SAT

High School

Let's consider the information given:

⇒ we have a 3 digit number

⇒ it can only have one '1' within it

Let's consider the possibilities:

⇒ 1 _ _

⇒ the tens digit has 9 choices of number 0 ⇔9 except 1

⇒ the ones digit has 9 choices of number 0⇔9 except 1

Total choices (in this case) = 9 * 9 = 81

⇒ _ 1 _

⇒ the hundred digit has 8 choices '0 ⇔ 9' except 0 and 1

⇒ ones digit has 9 choices 0 ⇔ 9 except 1

Total choices (in this case) = 8 * 9 = 72

⇒ _ _ 1

⇒ the hundreds digit has 8 choices 0 ⇔ 9 except 0 and 1

Overall Total choices = 81 + 72 + 72 = 81 + 144 = 225

Hope that helps!

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Let's consider the information given:⇒ we have a 3 digit number

⇒ it can only have one '1' within it

Let's consider the possibilities:⇒ 1 _ _

⇒ the tens digit has 9 choices of number 0 ⇔9 except 1

⇒ the ones digit has 9 choices of number 0⇔9 except 1

Total choices(in this case) =9 * 9 = 81⇒ _ 1 _

⇒ the hundred digit has 8 choices '0 ⇔ 9' except 0 and 1

⇒ ones digit has 9 choices 0 ⇔ 9 except 1

Total choices(in this case) =8 * 9 = 72⇒ _ _ 1

⇒ the hundreds digit has 8 choices 0 ⇔ 9 except 0 and 1

⇒ ones digit has 9 choices 0 ⇔ 9 except 1

Total choices(in this case) =8 * 9 = 72Overall Total choices = 81 + 72 + 72 = 81 + 144 = 225Hope that helps!