Arrange the following alkenes in order of decreasing stability

1) 1-pentene

2) Cis-2-pentene

3) Trans-2- pentene

4) 2-methyl-2-pentene

1) has 2 $\mathrm{\alpha }$-hydrogens, 2) and 3) have 5 $\mathrm{\alpha }$-hydrogens each while 4) has 8 $\mathrm{\alpha }$-hydrogens. More the number of $\mathrm{\alpha }$-hydrogens, more will be the number of hyperconjugative structures and more will be the stability. Moreover, trans isomer is more stable than cis isomer on account of steric hindrance.