AC Lim's answer to SlyFox's Secondary 1 Maths Singapore question.
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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
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
Date Posted:
5 years ago
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