If the projection of the vector i +2 j + k on the sum of the two vectors 2 i +4 j -5 k and -λ i +2 j +3 k is 1, then λ is equal to \ \ \ \.

If the projection of the vector $\displaystyle \hat{i}+2 \hat{j}+\hat{k}$ on the sum of the two vectors $\displaystyle 2 \hat{i}+4 \hat{j}-5 \hat{k}$ and $\displaystyle -\lambda \hat{i}+2 \hat{j}+3 \hat{k}$ is $\displaystyle 1$ , then $\displaystyle \lambda$ is equal to \_\_\_\_.