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01/11/2017 at 13:44
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Angie is purchasing stickers to make house numbers for the houses in her neighborhood. If the houses are numbered consecutively from 101 to 250 and each sticker contains a single digit, how many stickers containing the digit 3 does Angie need to purchase? 



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    Lê Quốc Trần Anh Coordinator 01/11/2017 at 16:33

    From 101 to 199 (except from 130 to 139) she needs: \(1\cdot9=9\left(sers\right)\)

    From 130 to 139 she needs: \(1\cdot10+1=11\left(sers\right)\)

    From 200 to 250 (except from 230 to 239) she needs: \(1\cdot4=4\left(sers\right)\)

    From 230 to 239 she needs: \(1\cdot10+1=11\left(sers\right)\)

    So she need to purchase: \(11+4+11=26\left(sers\right)\)

    ANSWER: 26 sers

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    Công Đinh 02/11/2017 at 19:34

    From 101 to 199 (except from 130 to 139) she needs: 1⋅9=9(sers)

    From 130 to 139 she needs: 1⋅10+1=11(sers)

    From 200 to 250 (except from 230 to 239) she needs: 1⋅4=4(sers)

    From 230 to 239 she needs: 1⋅10+1=11(sers)

    So she need to purchase: 11+4+11=26(sers)

    ANSWER: 26 sers



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