SAMN = 2/3 × SNAB = 2/3 × 1/3 × SABC
= 2/9 × SABC = 40 (cm2)
SBMQ = 1/2 × SMBC = 1/2 × 1/3 × SABC
= 1/6 × SABC = 30 (cm2)
SCPQ = 1/2 × SPBC = 1/2 × 1/3 × SABC
= 1/6 × SABC = 30 (cm2)
SMNPQ = 240 − 40 − 30 − 30 = 140 (cm2)
Đáp số: 140 cm2