A body travels 200 cm in the first2 s and 220 cm in the next 4 s with deceleration. The velocity of the body at the end of the seventh second is

$200=\mathrm{u}\times 2-(1/2)\mathrm{a}(2{)}^2$
or $\mathrm{u}-\mathrm{a}=100$………..(1)
$200+220=\mathrm{u}(2+4)-(1/2)(2+4{)}^2\mathrm{a}$
or $\mathrm{u}-3\mathrm{a}=70$…………(2)
Solving Eqs (i) and (ii), we get $\mathrm{a}=15{\mathrm{cms}}^{-2}\text{ and }\mathrm{u}=115{\mathrm{cms}}^{-1}$
Further, $\mathrm{v}=\mathrm{u}-\mathrm{at}=115-15\times 7=10{\mathrm{cms}}^{-1}$