posted by Aliza on .
It's about arithmetic sequence . . (the sum) SOLUTION PLEASE THANK YOU SO MUCH
1. A runner begins training on July 1 by running a kilometer, and increases the length of the run by 0.2 km/day. Find the length ofthe run in July 18 .
2.Bowling pins are set up in four rows with one pin in the first row, two pins in the second row, three pins in the third and four in the last. Suppose a gigantic set of pins was set up in 15 rows, the first row having one pin and each successive row having one more, so that the last row has 15 pins. How many pins would you have to knock over to make a strike ?
3. Stella has 100.00 in her pigggy bank. She puts 10 in it and each successive weeks she puts 10.00 more than what she put the week before. How much is in the liggy bank after six months ?
4. A contractor pays 120.00 penalty for the first extra day she takes to complete a job. The daily charge in increased 30.00 each extra day thereafter. what is the total penalty if she takes 6 extra days ?
5. How many times will a clock strike in one day if it strikes every hour, once at 1 , twice at 2 , thrice at 3,...?
6 Without using a formula, write a letter to your classmate explaining how to use a shortcut to find the sum of the whole numbers from 1-60
1. On day n,
Tn = 1+0.2(n-1) = 1+.2n-.2 = 0.8 + 0.2n
So, on July 18 (day 18) T18 = 0.8+0.2*17 = 4.2 km
2. Tn = n
Sn = n/2 (1 + n) = n(n+1)/2
S15 = 15*16/2 = 120
Try the others. Just thinks about how the sequence increases, and work out the formula. Where does it start? How fast does it grow? Come on back if you get stuck.