(seven out of eight) (guess an idiom) (seven ups and downs)

eight

1× 1 (guess an idiom) (unchanged (homophonic: one time unchanged))

2, 4, 6, 8, 10 (to use an idiom): coincidence.

1 2 5 6 7 (to use an idiom) (forgetting things)

1000 *1000 =100 *100 (as an idiom) (of course)