deb has 25 buttons. her grandmother gives her more buttons. then deb gives her sister 11 buttons. now deb has 57 buttons. how ma
1 answer:
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Answer:
481
Step-by-step explanation:
There are several ways you can get there.
1. There are only 13 numbers, so you can write them down and add them up.
25 + 27 + 29 + ... + 47 + 49 = 481
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2. You can use the formula for the sum of an arithmetic sequence. This one has a starting value of 25, an ending value of 49, and 13 terms.
Sum = ((start) + (end))/2 × (number of terms) = (25 +49)/2×13 = 481
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3. You can use a formula for the terms of the series and evaluate the sum.
an = 25 +2(n -1) = 2n +23