Question

what is the formula of 1,2 3,4.........n​

Answer 1

$\sf \: If a:b=5:9 and b:c=4:7 \\ \\ \sf</p><p>Make the value of "b" for both the \\ \sf ratio equal by multiplying 4 to 5:9 and 9 to 4:7. \\ \\ \sf</p><p>So,a:b=20:36 and b:c=36:63 \\ \\ \sf</p><p>Then,a:b:c=20:36:63 (Required answer).$

Answer 2

Answer:

n(n+1)/2

Step-by-step explanation:

usually 1,23,4,.....n =n(n+1)/2