In the locus diagrams of two projectiles I and 2 as shown in the fig.,

Both projectiles have same height.∴ H1 = H2(u1sin θ1)22g = (u2sinθ2)22gu1sin θ1 = u2sin θ22u1sin θ1g = 2u2sin θ2g ⇒ T1 = T2Now u1u2 = sin θ2sin θ1   sin θ1 > θ2sin θ1sin θ2 > 1 ⇒ u1u2 <1