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primary 5 | Maths
| Fractions
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Please solve the problem
Date Posted: 2 years ago
Views: 722
fig 1 → 1
fig 2 → 1+2
fig 3 → 1+2+3
...
fig n → n•(n+1)÷2
(a) n = 5
5×(5+1)÷2 = 15 (Ans)
(b) n = 13
13×(13+1)÷2 = 91 (Ans)
(c) 55
2×55 = 110
10×(10+1)= 110
Ans : fig 10
fig 2 → 1+2
fig 3 → 1+2+3
...
fig n → n•(n+1)÷2
(a) n = 5
5×(5+1)÷2 = 15 (Ans)
(b) n = 13
13×(13+1)÷2 = 91 (Ans)
(c) 55
2×55 = 110
10×(10+1)= 110
Ans : fig 10
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done
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https://en.wikipedia.org/wiki/1_%2B_2_%2B_3_%2B_4_%2B_%E2%8B%AF
Date Posted:
2 years ago
https://betterexplained.com/articles/techniques-for-adding-the-numbers-1-to-100/
Thanks a lot
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