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Secondary 1 | Maths
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SlyFox
SlyFox

Secondary 1 chevron_right Maths chevron_right Singapore

I need help with b) and c). Thank you!

Date Posted: 5 years ago
Views: 826
AC Lim
AC Lim
5 years ago
b) ratio red : total = 1:2
c) From answer a), total dot/2 is equal to red dot.
Total dot = n x n+1
Red dot = total dot/2 = n(n+1)/2
Formula for 1+2+3....+n
1 =1
1+2 =3
1+2+3 = 6
.
.
.

n (n+1)/2
d) sum 51 to 200 = sum 1 to 200 - sum 1 to 50
Sum 1 to 200 = 200 x (200+1)/2 = 20100
Sum 1 to 50 = 50 x (50+1)/2 = 1275
Therefore, sum 51 to 200 = 20100-1275=18825

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Joshua Ignatius Koh Jun Min
Joshua Ignatius Koh Jun Min's answer
11 answers (Tutor Details)
1st
b) ratio red : total = 1:2
c) From answer a), total dot/2 is equal to red dot.
Total dot = n x n+1
Red dot = total dot/2 = n(n+1)/2
Formula for 1+2+3....+n
1 =1
1+2 =3
1+2+3 = 6
.
.
.

n (n+1)/2
d) sum 51 to 200 = sum 1 to 200 - sum 1 to 50
Sum 1 to 200 = 200 x (200+1)/2 = 20100
Sum 1 to 50 = 50 x (50+1)/2 = 1275
Therefore, sum 51 to 200 = 20100-1275=18825
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AC Lim
Ac Lim's answer
13073 answers (A Helpful Person)
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syjiaxuan
Syjiaxuan's answer
290 answers (A Helpful Person)
Hope this helps, parts in pink are impt
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syjiaxuan
Syjiaxuan's answer
290 answers (A Helpful Person)
Hope this helps, parts in pink are impt