Help with the formula for mean germination time

[nisidotatos]

Hello guys, we are doing at college an experiment with the germination of some seeds.
We have generated some date and would like to calculate the mean germination time with excel.
THe formula for that is

• MGT= ∑(T₁*n₁ + T₂*n₂ +…+ T_k*n_k)/∑(n₁ + n₂ +…+n_k)

where - n= no. of new germinated seed, T= time from the beginning of the experiment

	time in hours	number of germinated seeds
	12	0
	24	2
	36	17
	48	11
	60	38
	72	17
	84	1
	96	0
	108	1
	120	1
	132	0
	144	0
	156	0
	168	0
	180	1
	192	0

<tbody>
</tbody>

So if i wanted to calculate the MGT in the cell below the numbers of germinated seeds how could i write this formula so that excel would accept it?

Best regards
Panos

 

[BGY23]

Hours in col E Seeds in F


=SUMPRODUCT(E3:E18,F3:F18)/SUM(F3:F18)

 

[nisidotatos]

hello again,
i am trying with this formula : =SUMPRODUCT(B8:C8,B9:C9,B10:C10,B11:C11,B12:C12,B13:C13,B14:C14,B15:C15,B16:C16,B17:C17,B18:C18,B19:C19,B20:C20,B21:C21,B22:C22,B23:C23)/SUM(C8:C23)
but i dont get a number. all i get is

4.3464E+28 .......

<tbody>
</tbody>