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primary 6 | Maths | Data Analysis
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Elly
Elly

primary 6 chevron_right Maths chevron_right Data analysis chevron_right Singapore

I am confusion

Date Posted: 5 years ago
Views: 269
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Sum the last 50 number...
Add 351+352+353+......397+398+399+400
1. 351+400= 751
2. 352+399= 751
3. ...
4......
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25. 375+376 = 751
So, sum = 25.x 751= 18775.
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AC Lim
Ac Lim's answer
13120 answers (A Helpful Person)
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Elly
Elly
5 years ago
That's a lot of numbers to calculate (๑•﹏•) Is there any other way to solve this?
AC Lim
AC Lim
5 years ago
Yes.
Can use formula: nx(n+1)/2

For this u have to do 2 step
1. Add from 1 to 400
2. Then minus sum from 1 to 350

Here we go....
1. 400x401/2= 80200
2. 350x351/2= 61425

Therefore sum 351 to 400
= 80200-61425= 18775.

Hope you can digest
Elly
Elly
5 years ago
Yes, I understand now...thanks