What is the solution for 2.3.4.15.12 3.4.5.28.20 4.5.6.45.30 5.6.7.66.42 6.7.8. .56 what is?

Answer 1

The missing number is 91. The pattern is looking at the sequence in blocks of five numbers.

The first three numbers in each block follow the pattern 2.3.4, 3.4.5, 4.5.6, 5.6.7, 6.7.8, ..... i.e. each subsequent triple starts with the middle number of the preceding triple, and continues counting order for the remaining two numbers in the triple.

The fifth number in each block is the product of the second and third numbers of that block ; i.e. 3(4)=12, 4(5) = 20, 5(6)=30, 6(7)=42, 7(8)= 56,....

The fourth number in each block is the product of the second number and a number in the sequence of consecutive odd numbers starting with 5; i.e. 3(5)=15; 4(7)=28; 5(9)=45, 6(11)=66, 7(13)=91,...